Laser marking system and method

Abstract

A laser marking system for marking a product comprising a laser source (110) configured to generate blue radiation; a marking head (120) configured to project the blue radiation on to the product (130); and, an optical fiber (140) configured to transmit the blue radiation from the laser source to the marking head.

Description

Laser marking system and methodTECHNICAL FIELD

[0001] The present disclosure relates to a laser marking system, method and a laser source involving the generation and use of blue electromagnetic radiation. Aspects and implementations of the present disclosure are directed generally to laser marking equipment and methods.BACKGROUND

[0002] Known laser marking systems typically utilize infrared radiation generated by a CO2 laser source for marking products.

[0003] It is in object of the present invention to provide a laser marking system and method that obviates or mitigates one or more problems of the prior art whether identified herein or elsewhere.SUMMARY

[0004] According to a first aspect of the present disclosure, there is provided a laser marking system for marking a product. The laser marking system comprises a laser source configured to generate blue radiation. The laser marking system comprises a marking head configured to project the blue radiation on to the product. The laser marking system comprises an optical fiber configured to transmit the blue radiation from the laser source to the marking head.

[0005] Any of the following features of the first aspect of the present disclosure may be combined, whether alone or in any combination, with any of the second to eleventh aspects of the present disclosure.

[0006] CO2 laser sources are commonly used for laser marking applications. CO2 lasers produce infrared radiation, e.g. having a wavelength of about 10 pm, which is absorbed well by most products (such as, for example, packaging materials) for marking applications. However, known CO2 lasers are bulky and are therefore difficult to integrate into production lines.

[0007] Blue radiation may have a wavelength of about 400 nm or more. Blue radiation may have a wavelength of about 470 nm or less.

[0008] It has been realised that blue laser radiation (e.g. in the inclusive spectral range of about 400 nm to about 470 nm) can be used to mark products for which CO2 lasers are often used.

[0009] Blue laser sources, such as laser diodes, are advantageously more compact than CO2 laser sources.

[0010] Blue laser sources, such as laser diodes, are advantageously more energy efficient than CO2 laser sources. For example, CO2 lasers may have an energy efficiency of between about 5% and 10%, whereas blue radiation sources such as a laser diode may have an energy efficiency of about 25% or more, e.g. about 30%.

[0011] Blue laser sources, such as laser diodes, are advantageously less expensive to produce, operate, and / or maintain compared to CO2 laser sources.

[0012] Blue laser sources, such as laser diodes, advantageously have a greater power stability than CO2 laser sources, which particularly improves marking on thinner products such as, for example, films. For example, known CO2 laser sources may experience power variations of ±10% or more, whereas blue laser sources such as laser diodes may experience power variations of ±1 % or less during operation. A blue laser diode may have a power stability that is five times greater, or more, than a CO2 laser source.

[0013] Blue laser sources, such as laser diodes, are simpler to operate than CO2 laser sources. For example, blue laser sources allow seamless adjustments of power without the need for complex techniques such as Pulse Width Modulation (PWM) chopping.

[0014] Blue laser sources, such as laser diodes, are faster to operate than CO2 laser sources. For example it is faster and easier to set desired laser parameters, thereby allowing operation of the laser marking system with less of a delay to set desired parameters compared to a CO2 based laser marking system.

[0015] Due to differences in photon energy and energy deposition efficiencies, blue radiation has been found to mark products faster than CO2 laser generated radiation, thereby allowing greater marking speeds and throughput of products compared to CO2 based laser marking systems when operated at the same or similar power.

[0016] Blue laser sources, such as laser diodes, have faster switching times between being off and on (i.e. rise and fall times) compared to CO2 laser sources. Laser marking typically involves switching the laser source off and on frequently. For example, the laser source may be switched on during marking of a first marking vector of a character, switched off during adjustment of the laser marking head in preparation for marking a second marking vector of the character (e.g. movement of beam steering mirrors), and then switched on again during marking of the second marking vector. For periods during which the laser source is to be switched on, a substantially full laser powermay be necessary in a relatively short time (e.g. in the order of 10 ps). As is the case for CO2 laser sources, if the laser power increases relatively slowly to the full power after the laser source is switched on, the first part of a character may not be marked or may suffer a reduced marking quality (e.g. reduced contrast) in the time it takes for the laser source to reach its full laser power. As is the case for CO2 laser sources, to make sure that the full laser power is available as quickly as possible (e.g. in periods of about 10 ps), the laser source may be operated close to a lasing threshold (i.e. a lowest excitation level at which the output is dominated by stimulated emission rather than spontaneous emission) of the laser source. This technique may be referred to in the art as “tickling” such that a laser beam with relatively low power (which may be referred to in the art as “leakage power”) is emitted by the laser source. For blue laser sources, because of the faster switching times available, no tickling is required which advantageously avoids leakage power issues associated with CO2 laser sources.

[0017] Given that CO2 laser sources take a relatively long time to reach full power after being switched on, users may utilise a shutter system (e.g. a galvanometer shutter or mechanical plate) configured to selectively block the laser light emitted by the CO2 laser source. This allows the CO2 laser source to be left switched on and thereby avoid the relatively long start up time whilst satisfying laser safety requirements. For blue laser sources, because of the faster switching times available, inclusion of a shutter system may be avoided, resulting in a more compact and less complex laser marking system. For example, the blue laser source may reach full power about 20 ps or less after being switched on.

[0018] A free space laser source involves the use of multiple combined laser diodes without sending the output beam of each laser diode through an optical fiber. Aligning the output beam of each laser diode is difficult and a beam quality of each laser diode varies leading to a generally poor beam profile (e.g. producing a non-circular beam profile having an inhomogenous energy distribution). Given these limitations, a free space laser source must be located very close to the marking head of a laser marking system to retain an acceptable beam quality at the product. Cooling the multiple laser diodes requires a large amount of space which must be taken up close to the marking head due to the alignment and beam quality limitations discussed above.

[0019] Use of an optical fiber avoids free space operation, and thereby advantageously avoids the associated drawbacks of free space operation.

[0020] The optical fiber allows a greater separation of the laser source and the marking head which enables a more compact marking head (e.g. heat removal apparatus can be located in the laser source rather than the marking head).

[0021] The optical fiber provides a substantially circular beam profile that can be used to mark in any direction.

[0022] The optical fiber provides a substantially homogenous beam power distribution which enables higher quality marking than CO2 laser marking systems.

[0023] The optical fiber provides a shared route of transmission for multiple blue laser sources and thereby avoids the limited focal range associated with alignment of a plurality of lasers operating in free space operation.

[0024] The optical fiber based laser marking system of the present disclosure has a focal range (i.e. a useable focal depth) that may be greater, e.g. about two times greater or more, than a focal range of known CO2 laser marking systems.

[0025] The optical fiber may be used to mix the blue radiation output by a plurality of laser sources into a single output beam that enjoys substantially uniform propagation downstream and upstream of a focal point of the marking head.

[0026] The laser marking system may be configured to output multimode blue radiation. The laser marking system may be configured to output single mode blue radiation. The laser marking system may be configured to output TEMoo mode blue radiation.

[0027] The optical fiber may be a solid core optical fiber. The solid core optical fiber may have a core diameter of about 200 pm or less, or about 105 pm or less, or about 50 pm or less, or about 5 pm.

[0028] Known laser cutting and welding systems utilize large core diameters of about 400 pm. This results in a relatively large focus spot of several millimetres, which is too large for many laser marking applications. Having a reduced core diameter advantageously provides a relatively small focus spot (e.g. about 200 pm) that is suitable for use in laser marking applications.

[0029] It has been found that using a reduced fibre core diameter for blue radiation advantageously solves or improves various beam profile issues. For example, a quality of the beam output by the optical fiber may be defined as follows:where M|naxeffectively compares a shape of the blue radiation beam to that of an ideal Gaussian beam for which M2= 1 , rcois a core radius of the optical fiber, NA is a numerical aperture of the optical fiber (which corresponds to a maximum divergenceangle of the blue radiation entering the optical fiber), and A is a wavelength of the blue radiation. Larger M|naxvalues (i.e. greater than 1) correspond to deviations from an ideal Gaussian beam. A M|naxvalue less than 1 cannot be achieved. Given this relationship, by reducing the core radius, the M|naxvalue also reduces proportionally, thereby approaching an ideal Gaussian beam (which can be understood as an improvement in beam quality). For example, by reducing the core diameter from about 105 pm to about 50 pm, the quality of the beam is more than doubled at about the same focus spot size.

[0030] Improving the beam quality may advantageously allow for one or more of an increase in a focal range or depth of the laser marking system. This may increase a tolerance of the laser marking system to changes in working distance due to, for example, a non-flat product and / or marking plane, thereby allowing marking quality to remain high despite said changes.

[0031] Improving the beam quality may advantageously allow for a diameter of the beam in the marking head to be reduced. This advantageously allows a size of the marking head and the components therein (e.g. galvanometer driven mirrors) to be reduced. Alternatively, by improving the beam quality whilst maintaining the diameter of the beam in the marking head, a working distance and a marking field area of the laser marking system are increased. This advantageously allows for marking of larger products at greater distances at faster marking speeds.

[0032] The optical fiber may be a hollow core optical fiber. The hollow core optical fiber may have a core diameter of about 500 pm or less.

[0033] The hollow core of the optical fiber may comprise a gas.

[0034] It has been found that using a hollow core optical fiber having a core diameter of about 500pm or less provides advantageous beam properties for laser marking purposes.

[0035] The optical fiber may have a numerical aperture within the inclusive range of about 0.1 to about 0.5.

[0036] The optical fiber may have a numerical aperture of about 0.22.

[0037] It has been found that using an optical fiber having a numerical aperture of about 0.1 to about 0.5 provides advantageous beam properties for laser marking purposes.

[0038] The laser marking system may comprise a coupling system configured to optically couple the optical fiber to an optical component.

[0039] The optical component may be the laser source.

[0040] The optical component may be the marking head.

[0041] The coupling system may be configured to adjust an angle of incidence between the blue radiation emitted by the laser source and an input of the optical fiber.

[0042] A beam profile of the blue electromagnetic radiation in the optical fiber and / or in the marking head and / or in a marking spot on a product may be changed by adjusting the angle of incidence between the blue radiation emitted by the laser source and the input of the optical fiber.

[0043] The coupling system may be configured to adjust a position of the blue radiation emitted by the laser source relative to an input of the optical fiber.

[0044] The coupling system may comprise a coupling lens configured to adjust a focus of the blue radiation emitted by the laser source before entering an input of the optical fiber.

[0045] The coupling system may comprise a first adjustable optical element configured to receive the blue radiation from the laser source. The coupling system may comprise a second adjustable optical element configured to receive the blue radiation from the first adjustable optical element and direct the blue radiation towards an input of the optical fiber.

[0046] The coupling system may comprise a first detector configured to detect a position of the blue radiation relative to the second adjustable optical element. The coupling system may comprise a second detector configured to detect a position of the blue radiation relative to the input of the optical fiber.

[0047] The coupling system may advantageously improve a coupling efficiency between the optical fiber and the laser source and / or the marking head, thereby improving an efficiency of the laser marking system.

[0048] The coupling system may comprise a coupling lens for optically coupling the optical fiber to the optical component. A ratio of a focal length to a diameter of an entrance pupil of the coupling lens may be selected in at least partial dependence on the following equation:where F# is the ratio of a focal length to a diameter of an entrance pupil of the coupling lens, Dcoreis a core diameter of the optical fiber, and A is a wavelength of the blue radiation.

[0049] It has been found that using such a coupling lens improves coupling efficiency of the blue radiation into the optical fiber, thereby improving an efficiency of the laser marking system.

[0050] The ratio of the focal length to the diameter of the entrance pupil of the coupling lens may be selected to be within about -5% and about +2% of a value of F# calculated in accordance with the equation above.

[0051] It has been found that using such a coupling lens improves coupling efficiency of the blue radiation into the optical fiber, thereby improving an efficiency of the laser marking system.

[0052] An end of the optical fiber may be tapered.

[0053] A tapered optical fiber advantageously improves a coupling efficiency between the optical fiber and the laser source and / or the marking head, thereby improving an efficiency of the laser marking system.

[0054] The optical fiber may comprise an end cap. The end cap may be a core-less end cap. The end caps may comprise a substantially transparent glass pieces which lack a waveguide. The blue radiation may therefore expand when propagating through the end cap. As such, a diameter of the blue radiation is increased before reaching an interface (e.g. a glass-air interface) at which damage may otherwise occur. By increasing the diameter and thereby reducing the intensity of the beam, the blue radiation may be transmitted without damaging the optical fiber. For example, end caps may be used for laser beams having a power of about 60 W or more to protect the optical fiber.

[0055] A length of the optical fiber may be about 15 m or less.

[0056] The length of the optical fiber may be, for example, about 10.75 m.

[0057] The laser marking system may be configured to output blue radiation having an annular beam profile.

[0058] The optical fiber may be configured to output blue radiation having a substantially annular beam profile. The optical fiber may be configured to convert a beam profile of the blue radiation generated by the laser source to an annular beam profile.

[0059] The laser marking system may comprise an optical element configured to change the beam profile received from the laser source to the annular beam profile. The optical element may comprise a diffractive optical element. The optical element may comprise an axicon.

[0060] It may be desirable to operate the laser marking system such that a relatively large beam spot is achieved at a relatively small working distance. The optical fiber may be configured to output a laser beam having a relatively poor quality, which in turn limits an ability of the beam to be focussed. This has been found to be advantageous for laser marking applications using blue radiation. It has been found that reducing a quality ofthe beam of blue radiation provides a relatively large beam spot at a relatively small working distance, which may be advantageous for laser marking purposes.

[0061] The optical fiber may be configured to output a laser beam having an M2factor of about 20 or more. The optical fiber may be configured to output a laser beam having an M2factor of about 40 or less. The optical fiber may be configured to output a laser beam having a beam parameter product of about 2.9 mm mrad or more. The optical fiber may be configured to output a laser beam having a beam parameter product of about 5.5 mm mrad or less.

[0062] The laser source may comprise a laser diode.

[0063] Laser diodes provide multiple advantages over traditional CO2 laser sources as discussed above.

[0064] The laser source may comprise a plurality of laser diodes.

[0065] Using a plurality of laser diodes advantageously increases a power stability of the laser marking system. This is because using multiple laser diodes averages out power variations associated with each individual laser diode of the plurality of laser diodes.

[0066] The laser source may be configured such that a number of the laser diodes is changeable.

[0067] Having a changeable number of laser diodes advantageously allows power scaling by adding or removing laser diodes.

[0068] Polarization coupling, such as incoherent polarization combining, may be used to couple a plurality of blue laser beams generated by a plurality of laser diodes into the optical fiber, and thereby power scale the laser source. Polarization beam combining may be used to combine two blue laser beam propagation paths having different (e.g. perpendicular) polarization orientations. Alternatively spatial beam combining or wavelength beam combining may be used. Spatial beam combining may be used to combine a plurality of laser diodes (e.g. up to about eight diodes). Spatial beam combining may comprise arranging a plurality of mirrors with respect to a plurality of laser diodes. Each laser diode may have its own associated mirror configured to reflect the blue radiation emitted by the laser diode onto a common propagation path. The laser diodes and mirrors may be arranged to form a plurality of rows. The mirrors of each row may be slightly offset from each other such that blue radiation reflected by one of the mirrors is not blocked by a different mirror in the row. Each mirror may be adjustable such that each beam reflected from each mirror has substantially the same angular propagation direction. As such, all blue radiation beams generated by theplurality of laser diodes propagate along a common path having substantially the same propagation angle, and so may be considered to be spatially combined. Wavelength beam combining may comprise sorting laser diodes by their wavelength or operating the laser diodes such that they operate at substantially the same wavelength. A wavelength beam combiner comprising one or more coatings and / or grids may be used to transmit or reflect certain wavelengths of radiation. For example, some coatings may be configured to transmit blue radiation having a wavelength of about 440 nm and reflect blue radiation having a wavelength of about 443 nm. Laser diodes emitting 440 nm blue radiation may be combined via transmission through the coatings whilst laser diodes emitting 443 nm blue radiation may be combined via reflection from the coatings.

[0069] The plurality of laser diodes may be configured to operate below a maximum power rating of the plurality of laser diodes.

[0070] Operating below a maximum power rating of the plurality of laser diodes advantageously prolongs an operational lifetime of the laser diodes whilst the number of laser diodes present can be selected to reach a desired power level for a given laser marking application (e.g. to reach a desired marking speed). It has been found that the decrease in operating power of the laser diodes is not directly proportional to the associated increase in operational lifetime of the laser diodes, but instead causes a greater increase in the operational lifetime of the laser diodes. For example, decreasing the operating power of the laser diodes by a first factor may increase the operational lifetime of the diodes by a greater factor, resulting in a much greater benefit than expected.

[0071] The laser source may be configured to generate blue radiation having a power within the inclusive range of about 1 W to about 200 W.

[0072] The laser marking system may be configured to provide blue radiation having a power of about 30W.

[0073] It has been found that providing blue radiation having a power within the inclusive range of about 1 W to about 200 W advantageously improves laser marking applications.

[0074] The laser source may be configured to generate continuous wave blue radiation.

[0075] It has been found that some materials are less likely to be damaged by continuous wave blue radiation compared to a pulsed radiation. For example, packaging foil may comprise an aluminium layer which may be very easily damaged by pulsed laserradiation. However, it has been found that continuous wave blue radiation is less likely to damage the aluminium layer.

[0076] The marking head may be configured to project the blue radiation such that the blue radiation has a focal spot diameter within the inclusive range of about 10 pm to about 1000 pm.

[0077] The marking head may be configured to project the blue radiation such that the blue radiation has a focal spot diameter within the inclusive range of about 200 pm to about 550 pm.

[0078] The marking head may be configured to project the blue radiation such that the blue radiation has a focal spot diameter of about 200 pm or more. The marking head may be configured to project the blue radiation such that the blue radiation has a focal spot diameter of about 550 pm or less.

[0079] It has been found that providing blue radiation having a focal spot diameter within the inclusive range of about 10 pm to about 1000 pm advantageously improves laser marking applications.

[0080] Focal spot diameter may be understood as a beam diameter of the blue radiation at or proximate a focal plane of the marking head.

[0081] Focal spot diameter may be understood as a beam diameter of the blue radiation within a working distance range of the marking head.

[0082] Focal spot diameter may be understood as a smallest beam diameter of the blue radiation.

[0083] The laser marking system may be configured to have a focal depth within the inclusive range of about 4 mm to about 35 mm.

[0084] The laser marking system may be configured to have a focal depth range of about 4 mm or more. The laser marking system may be configured to have a focal depth range of about 35 mm or less. The laser marking system may be configured to have a focal depth range of about 40 mm or less.

[0085] The focal depth range may be understood as a range of distances between the marking head and the product across which the blue radiation is in focus such that a mark may be formed as desired on the product. Having such a large focal depth range advantageously increases an adaptability of the laser marking system to different laser marking applications.

[0086] A diffractive optical element may be incorporated into the laser marking system to increase a focal depth range of the laser marking system. For example, the diffractive optical element may be configured to increase the focal depth range of thelaser marking system beyond 35 mm. The diffractive optical element may be configured to output blue radiation having a Bessel beam profile.

[0087] The marking head may be configured to operate at a working distance within the inclusive range of about 5 mm to about 1000 mm.

[0088] The working distance of the marking head may be within the inclusive range of about 18 mm to about 192 mm.

[0089] The working distance of the marking head may be about 18 mm or more. The working distance of the marking head may be about 192 mm or less. The working distance of the marking head may be about 140 mm or less.

[0090] The working distance of the marking head may be understood as a distance between an optical output of the marking head (e.g. a window through which the blue radiation exits the marking head) and a marking plane at which the blue radiation is in focus.

[0091] The working distance of the marking head may be understood as a distance between a reference point on the marking head or optic to the focal point or spot of the laser marking system.

[0092] The working distance may be a range, i.e. a working distance range, for marking at multiple distances or z positions.

[0093] The laser marking system may be configured to operate at a marking speed within the inclusive range of about 1 mm s-1to about 20000 mm s’1.

[0094] The marking head may comprise a focusing lens configured to receive expanding blue radiation emitted by the optical fiber. A propagation distance between an output of the optical fiber and the focusing lens may be such that the blue radiation has a beam diameter within the inclusive range of about 0.5 mm to about 50 mm at the focusing lens.

[0095] The propagation distance between the output of the optical fiber and the focussing lens may be such that the blue radiation has a beam diameter of about 8mm at the focussing lens.

[0096] The optical fiber outputs an expanding beam. By setting the propagation distance between the output of the optical fiber and the focusing lens, the beam may expand to desired diameter before being focussed by the focusing lens to a desired spot size on the product to be marked.

[0097] The marking head may comprise a collimator configured to receive the blue radiation transmitted to the marking head by the optical fiber. The marking head may comprise a first lens configured to receive the blue radiation output by the collimator andexpand the blue radiation. The marking head may comprise a second lens configured to receive the blue radiation expanded by the first lens and focus the blue radiation.

[0098] The collimator may be configured to output the blue radiation having a beam diameter within the inclusive range of about 0.1 mm to about 15 mm.

[0099] The collimator may be configured to output the blue radiation having a beam diameter within the inclusive range of about 0.1 mm to about 5 mm.[000100] The collimator may be configured to output the blue radiation having a beam diameter of about 2.5 mm.[000101] The first lens may have a focal length within the inclusive range of about -5 mm to about -150 mm.[000102] The first lens may have a focal length of about -24.06 mm.[000103] The first lens may have a focal length of about -12.9 mm.[000104] The first lens may be configured to expand the blue radiation such that the blue radiation has a beam diameter within the inclusive range of about 0.5 mm to about 50 mm at the second lens.[000105] The first lens may be configured to expand the blue radiation such that the blue radiation has a beam diameter of about 8 mm at the second lens.[000106] The first lens may have a centre thickness within the inclusive range of about 0.5 mm to about 10 mm.[000107] The first lens may have a centre thickness of about 2 mm.[000108] The first lens may have an edge thickness within the inclusive range of about 1 mm to about 10 mm.[000109] The first lens may have an edge thickness of about 3.5 mm.[000110] A propagation distance between the collimator and the first lens may be within the inclusive range of about 1 mm to about 100 mm.[000111] The propagation distance between the collimator and the first lens may be about 4 mm.[000112] The second lens may have a focal length within the inclusive range of about 10 mm to about 1000 mm.[000113] The second lens may have a focal length within the inclusive range of about 27.5 mm to about 33.2 mm.[000114] The second lens may have a focal length of about 38.23 mm.[000115] Smaller focal lengths of the second lens may result from having a divergent beam entering the second lens (i.e. the focusing lens). In embodiments in which there is no first lens acting to expand the blue radiation before the blue radiation is incident uponthe second lens, and instead a collimated beam exiting the collimator is incident upon the second lens (i.e. the focusing lens), longer focal lengths of the second lens may be used.[000116] The second lens may have a centre thickness within the inclusive range of about 0.5 mm to about 15 mm.[000117] The second lens may have a centre thickness of about 3 mm.[000118] The second lens may have an edge thickness within the inclusive range of about 0.1 mm to about 15 mm.[000119] The second lens may have an edge thickness of about 3.0 mm.[000120] A propagation distance between the first lens and the second lens may be within the inclusive range of about 5 mm to about 150 mm.[000121] The propagation distance between the first lens and the second lens may be about 23.8 mm.[000122] A propagation distance between the second lens and a focal spot of the marking head may be within the inclusive range of about 10 mm to about 1000 mm.[000123] The propagation distance between the second lens and the focal spot of the marking head (i.e. at the product) may be within the inclusive range of about 88 mm to about 192 mm.[000124] At least one of the first and second lenses may comprise Suprasil 2A. Other types of glass may be used. However, it has been found that Suprasil provides superior performance for blue radiation laser marking purposes.[000125] The marking head may comprise a folding mirror located between the first lens and the second lens.[000126] A distance between the folding mirror and the first lens may be within the inclusive range of about 3 mm to about 150 mm.[000127] The distance between the folding mirror and the first lens may be about 21.554 mm.[000128] A distance between the folding mirror and the second lens may be within the inclusive range of about 3 mm to about 150 mm.[000129] The distance between the folding mirror and the second lens may be about 5.800 mm.[000130] The marking head may comprise a collimator configured to receive blue radiation transmitted to the marking head by the optical fiber. The marking head may comprise a focusing lens. The collimator may comprise a final lens configured to expandthe blue radiation. The focusing lens may be configured to receive the blue radiation expanded by the final lens and focus the blue radiation.[000131] A focal length of the final lens and a propagation distance between the final lens and the focusing lens may be such that the blue radiation has a beam diameter within the inclusive range of about 0.5 mm to about 50 mm at the focusing lens.[000132] The marking head may comprise an electromagnetic radiation steering mechanism configured to steer the blue radiation to address a specific location within a two-dimensional field of view. The electromagnetic radiation steering mechanism may comprise a first optical element having an associated first actuator configured to rotate the first optical element about a first rotational axis to change a first coordinate of a first steering axis in the two-dimensional field of view. The electromagnetic radiation steering mechanism may comprise a second optical element having an associated second actuator configured to rotate the second optical element about a second rotational axis to change a second coordinate of a second steering axis in the two-dimensional field of view. The electromagnetic radiation steering mechanism may comprise an electromagnetic radiation manipulator optically disposed between the first and second optical elements. A first angle may be defined between the first and second rotational axes. A second angle may be defined between the first and second steering axes. The electromagnetic radiation manipulator may be configured to introduce a difference between the first angle and the second angle.[000133] The first rotational axis and the second rotational axis may be non-orthogonal. [000134] The first rotational axis and the second rotational axis may be substantially parallel.[000135] The first steering axis and the second steering axis may be substantially orthogonal.[000136] The electromagnetic radiation manipulator may comprise a first mirror and a second mirror that are fixed with respect to each other.[000137] At least one of the first actuator and second actuator may comprise a galvanometer motor.[000138] Using a galvanometer motor advantageously provides fast beam direction control whilst avoiding the use of bulky x-y actuation stages such as those associated with laser cutting and laser welding systems.[000139] The laser marking system may comprise a housing configured to house the laser source. The optical fiber may connect the housing to the marking head such thatblue radiation generated in the housing is transmitted through the optical fiber before reaching the marking head.[000140] Locating the laser source outside of the marking head advantageously allows for a reduction in the size of the marking head for easier integration into production lines. [000141] The housing may comprise a cooling system configured to cool the laser source.[000142] Cooling systems are typically bulky. Locating the cooling system in the housing separate from the marking head advantageously allows for a more compact marking head that can be more easily integrated into production lines.[000143] The laser marking system may comprise a mode scrambler configured to mix different modes of blue radiation in the optical fiber.[000144] Using a mode scrambler advantageously improves a homogeneity of the blue radiation output by the laser marking system, which in turn improves a laser marking quality of the laser marking system.[000145] According to a second aspect of the present disclosure, there is provided a method of retrofitting a production system comprising a continuous inkjet marking system comprising replacing the continuous inkjet marking system with the laser marking system discussed above.[000146] The laser marking system of the present disclosure has been found to have a similar form factor, shape, size, applicability and operate at similar working distances to known continuous inkjet marking systems, which allows for a simple and quick replacement of the known continuous inkjet marking systems with the laser marking system of the present disclosure.[000147] According to a third aspect of the present disclosure, there is provided a method of marking a product comprising generating blue radiation. The method comprises transmitting the blue radiation through an optical fiber. The method comprises projecting the blue radiation on to the product.[000148] The method may comprise generating multimode blue radiation.[000149] The method may comprise projecting the blue radiation such that the blue radiation has a focal spot diameter of about 200 pm or more. The method may comprise projecting the blue radiation such that the blue radiation has a focal spot diameter of about 550 pm or less.[000150] The method may comprise using the optical fiber to output a laser beam having an M2factor of about 20 or more. The method may comprise using the optical fiber to output a laser beam having an M2factor of about 40 or less. The method maycomprise using the optical fiber to output a laser beam having a beam parameter product of about 2.9 mm mrad or more. The method may comprise using the optical fiber to output a laser beam having a beam parameter product of about 5.5 mm mrad or less.[000151] The method may comprise using a plurality of laser diodes to generate the blue radiation. The method may comprise using the optical fiber to collect the blue radiation generated by the plurality of laser diodes.[000152] The method may comprise using spatial beam combining to combine the blue radiation generated by the plurality of laser diodes.[000153] The method may comprise using polarization beam combining to combine the blue radiation generated by the plurality of laser diodes.[000154] The method may comprise generating continuous wave blue radiation.[000155] According to a fourth aspect of the present disclosure, there is provided a method of manufacturing a laser marking system comprising optically coupling a first end of an optical fiber to a laser source configured to generate blue radiation. The method comprises optically coupling a second end of the optical fiber to a marking head configured to project the blue radiation on to a product.[000156] According to a fifth aspect of the present disclosure, there is provided a laser marking system configured to mark a film. The laser marking system comprises a laser source configured to generate blue radiation. The laser marking system comprises a marking head configured to project the blue radiation on to the film when the film is located at a working distance of the marking head.[000157] Any of the following features of the fifth aspect of the present disclosure may be combined, whether alone or in any combination, with any of the first to fourth and sixth to eleventh aspects of the present disclosure.[000158] The film may comprise at least one of a plastic, a metal, a textile and a paper. [000159] The film may comprise any combination of the plastic, the metal, the textile and the paper.[000160] The film may comprise a plurality of layers. The plurality of layers may comprise individual layers of plastic and / or metal and / or textile and / or paper. The plurality of layers may comprise individual layers formed of different plastics.[000161] The plastic may comprise one or any combination of polyethylene, polypropylene, polystyrene, polyethylene Terephthalate, polyvinyl-chloride.[000162] The metal may comprise aluminium.[000163] The film may have a thickness within the inclusive range of about 20 pm to about 1000 pm.[000164] The film may have a thickness within the inclusive range of about 50 pm to about 200 pm.[000165] The film may comprise different layers (e.g. plastics, inks, barrier layers to prevent certain gases from diffusion through the film, etc.).[000166] The film may comprise ink.[000167] It has been found that whilst blue radiation may not be strongly absorbed by many film base materials, blue radiation is strongly absorbed by ink within the film. This advantageously allows high quality marking through alteration of the ink whilst the base material is not damaged by the blue radiation.[000168] The film may be flexible.[000169] The laser marking system may be configured to provide blue radiation having a power within the inclusive range of about 1 W to about 200 W.[000170] The laser marking system may be configured to provide blue radiation having a power of about 60 W or less.[000171] The marking head may be configured to project the blue radiation such that the blue radiation has a focal spot diameter within the inclusive range of about 10 pm to about 1000 pm.[000172] The laser marking system may have a focal depth range of about 4 mm to about 35 mm.[000173] A diffractive optical element may be incorporated into the laser marking system to increase a focal depth range of the laser marking system. The diffractive optical element may be configured to output blue radiation having a Bessel beam profile. [000174] The marking head may be configured to operate at a working distance within the inclusive range of about 5 mm to about 1000 mm.[000175] The laser marking system may be configured to mark the film at a marking speed within the inclusive range of about 1 mm s-1to about 20000 mm s-1[000176] Due to differences in photon energy and energy deposition efficiencies, blue radiation has been found to mark products faster than CO2 laser generated radiation, thereby allowing greater marking speeds and throughput of products compared to CO2 based laser marking systems.[000177] The laser source may comprise a laser diode.[000178] The laser source may comprise a plurality of laser diodes.[000179] The laser source may be configured such that a number of the laser diodes is changeable.[000180] The plurality of laser diodes may be configured to operate below a maximum power rating of the plurality of laser diodes.[000181] The laser source may be configured to generate blue radiation having a power that varies by 3% or less once a predetermined power and operating temperature are reached.[000182] The laser source may be configured to generate blue radiation having a power that varies by 2% or less once a predetermined power and operating temperature are reached.[000183] The laser source may be configured to generate blue radiation having a power that varies by 1 % or less once a predetermined power and operating temperature are reached.[000184] The predetermined power may comprise a predetermined power range. The operating temperature may comprise an operating temperature range.[000185] Known CO2 laser sources generate radiation having a power that varies by about 5% or more, e.g. about 10%, once a predetermined power and operating temperature are reached. The increased power stability of the blue laser source advantageously avoids or reduces the risk of damaging (e.g. unintentionally perforating) the film and / or poor quality marking that are associated with the greater power instability of known CO2 lasers.[000186] A sensor such as, for example, a thermopile sensor may be used to measure the power of the blue radiation. A suitable sensor may, for example, be a F150A-BB-26 Broadband 150 W Fan-Cooled Thermopile Sensor with 26 mm Aperture available from Ophir Optronics Solutions Ltd.[000187] The laser source may be configured to generate continuous wave blue radiation.[000188] A rise time of the laser source may be about 30 ps or less.[000189] The rise time of the laser source may be about 25 ps or less.[000190] The rise time of the laser source may be about 20 ps or less.[000191] The rise time of the laser source may be about 15 ps or less.[000192] The rise time of the laser source may be about 12 ps.[000193] CO2 laser sources have a rise time of about 35 ps or more, e.g. up to about 100 ps, which is significantly longer than the rise time of the laser source of the present disclosure. Longer rise times are associated with more frequent marking errors due to, for example, burning the product and / or fading at the beginning and / or end of individualmarks formed on the product. Reduced rise times advantageously avoid or reduce the frequency of said marking errors.[000194] A fall time of the laser source may be about 60 ps or less.[000195] The fall time of the laser source may be about 50 ps or less.[000196] The fall time of the laser source may be about 30 ps or less.[000197] The fall time of the laser source may be about 15 ps or less.[000198] The fall time of the laser source may be about 10 ps or less.[000199] The fall time of the laser source may be about 8 ps or less.[000200] The fall time of the laser source may be about 5 ps or less.[000201] The fall time of the laser source may be about 0 ps.[000202] CO2 laser sources have a fall time of about 68 ps or more, e.g. up to about 84 ps, which is significantly longer than the fall time of the laser source of the present disclosure. Longer fall times are associated with more frequent marking errors due to, for example, burning the product and / or fading at the beginning and / or end of individual marks formed on the product. Reduced fall times advantageously avoid or reduce the frequency of said marking errors.[000203] An end user of a CO2 based laser marking system may need to introduce delays such as, for example, adjusting a position of the steering mirrors in the marking head, between switching the CO2 laser source on and off to account for the relative large rise and / or fall times and thereby avoid or reduce the likelihood of marking errors. The laser source configured to generate blue radiation of the present disclosure does not suffer this drawback, thereby providing a less complex and more user friendly laser marking system that does not require the introduction of said delays.[000204] The laser marking system may be configured such that the blue radiation induces ablation and / or a chemical reaction on the film.[000205] The chemical reaction may comprising using the blue radiation to change a colour of the film.[000206] Marking with blue radiation may advantageously reduce the risk of ablating or otherwise damaging the film compared to marking with a CO2 laser.[000207] The marking head may comprise an electromagnetic radiation steering mechanism configured to steer the blue radiation to address a specific location within a two-dimensional field of view. The electromagnetic radiation steering mechanism may comprise a first optical element having an associated first actuator configured to rotate the first optical element about a first rotational axis to change a first coordinate of a first steering axis in the two-dimensional field of view. The electromagnetic radiation steeringmechanism may comprise a second optical element having an associated second actuator configured to rotate the second optical element about a second rotational axis to change a second coordinate of a second steering axis in the two-dimensional field of view. The electromagnetic radiation steering mechanism may comprise an electromagnetic radiation manipulator optically disposed between the first and second optical elements. A first angle may be defined between the first and second rotational axes. A second angle may be defined between the first and second steering axes. The electromagnetic radiation manipulator may be configured to introduce a difference between the first angle and the second angle.[000208] The first rotational axis and the second rotational axis may be non-orthogonal. [000209] The first steering axis and the second steering axis may be substantially orthogonal.[000210] The electromagnetic radiation manipulator may comprise a first mirror and a second mirror that are fixed with respect to each other.[000211] At least one of the first actuator and second actuator may comprise a galvanometer motor.[000212] According to a sixth aspect of the present disclosure, there is provided a method of retrofitting a production system comprising a continuous inkjet marking system comprising replacing the continuous inkjet marking system with the laser marking system discussed above.[000213] According to a seventh aspect of the present disclosure, there is provided a method of marking a film. The method comprises generating blue radiation. The method comprises projecting the blue radiation on to the film.[000214] Blue radiation sources have a greater power stability than CO2 laser sources. This reduced variation in power makes blue laser source better suited for marking films than CO2 laser sources. For example, a CO2 laser source may accidently penetrate the film if the power varies too high, or may fail to leave a legible mark on the film if the power varies too low. Blue laser sources, such as laser diodes, experience less power variation, and are therefore less likely to either penetrate the film and / or fail to leave a legible mark on the film compared to CO2 lasers.[000215] The method may comprise inducing ablation and / or a chemical reaction on the film.[000216] The chemical reaction may comprising using the blue radiation to change a colour of the film.[000217] Marking with blue radiation may advantageously reduce the risk of ablating or otherwise damaging the film compared to marking with a CO2 laser.[000218] The method may comprise inducing a colour change of the film.[000219] According to an eighth aspect of the present disclosure, there is provided a method of manufacturing a laser marking system comprising optically coupling a laser source configured to generate blue radiation to a marking head configured to project the blue radiation on to a film when the film is located at a working distance from the marking head.[000220] According to a ninth aspect of the present disclosure, there is provided a laser source for laser marking. The laser source comprises a plurality of laser diodes configured to generate blue radiation. The laser source comprises an optical fiber optically coupled to the plurality of laser diodes configured to collect the blue radiation generated by the plurality of laser diodes.[000221] Any of the following features of the ninth aspect of the present disclosure may be combined, whether alone or in any combination, with any of the first to eighth and tenth to eleventh aspects of the present disclosure.[000222] The laser source may comprise a coupling system configured to optically couple the plurality of laser diodes to the optical fiber.[000223] The coupling system may comprise a coupling lens configured to adjust a focus of the blue radiation emitted by the plurality of laser diodes before entering an input of the optical fiber.[000224] The coupling system may comprise a polarization beam combiner configured to combine blue radiation generated by the plurality of laser diodes.[000225] The polarization beam combiner may be configured to perform incoherent polarization combining, which may be used to couple a plurality of blue laser beams generated by the plurality of laser diodes into the optical fiber.[000226] The polarization beam combiner may comprise one or more wave plates, e.g. a quarter wave plate and / or a half wave plate, configured to change a polarization direction of the blue radiation generated by at least some of the plurality of laser diodes. [000227] The polarization beam combiner may comprise a beam combiner configured to transmit blue radiation (e.g. having a first polarization direction) generated by some laser diodes of the plurality of laser diodes and reflect blue radiation (e.g. having a different polarization direction) by other laser diodes of the plurality of laser diodes.[000228] The coupling system may comprise a wavelength beam combiner.[000229] The coupling system may comprise a spatial beam combiner. The spatial beam combiner may comprise an arrangement of a plurality of mirrors and a plurality of laser diodes. Each laser diode may have its own associated mirror configured to reflect the blue radiation emitted by the laser diode onto a common propagation path. The laser diodes and mirrors may be arranged to form a plurality of rows. The mirrors of each row may be slightly offset from each other such that blue radiation reflected by one of the mirrors is not blocked by a different mirror in the row. Each mirror may be adjustable such that each beam reflected from each mirror has substantially the same angular propagation direction. As such, all blue radiation beams generated by the plurality of laser diodes propagate along a common path having substantially the same propagation angle, and so may be considered to be spatially combined.[000230] The laser source may be configured such that a number of the laser diodes is changeable.[000231] Having a changeable number of laser diodes advantageously allows power scaling by adding or removing laser diodes.[000232] The plurality of laser diodes may be configured to operate below a maximum power rating of the plurality of laser diodes.[000233] Operating below a maximum power rating of the plurality of laser diodes advantageously prolongs an operational lifetime of the laser diodes whilst the number of laser diodes present can be selected to reach a desired power level for a given laser marking application (e.g. to reach a desired marking speed).[000234] The laser source may be configured to provide blue radiation having a power within the inclusive range of about 1 W to about 200 W.[000235] The laser source may be configured to provide blue radiation having a power of about 30W.[000236] The laser source may comprise a cooling system configured to cool the laser source.[000237] The laser source may be configured to generate blue radiation having a power that varies by 3% or less once a predetermined power and operating temperature are reached.[000238] The laser source may be configured to generate blue radiation having a power that varies by 2% or less once a predetermined power and operating temperature are reached.[000239] The laser source may be configured to generate blue radiation having a power that varies by 1 % or less once a predetermined power and operating temperature are reached.[000240] The predetermined power may comprise a predetermined power range. The operating temperature may comprise an operating temperature range.[000241] Known CO2 laser sources generate radiation having a power that varies by about 5% or more, e.g. about 10%, once a predetermined power and operating temperature are reached. The increased power stability of the blue laser source advantageously avoids or reduces the risk of damage to the product and / or poor quality marking that are associated with the greater power instability of known CO2 lasers.[000242] A sensor such as, for example, a thermopile sensor may be used to measure the power of the blue radiation. A suitable sensor may, for example, be a F150A-BB-26 Broadband 150 W Fan-Cooled Thermopile Sensor with 26 mm Aperture available from Ophir Optronics Solutions Ltd.[000243] The laser source may have an energy efficiency of about 15% or more.[000244] The laser source may have an energy efficiency of about 20% or more.[000245] The laser source may have an energy efficiency of about 25% or more.[000246] The laser source may have an energy efficiency of about 30% or more.[000247] Known CO2 laser sources have an energy efficiency of between about 5% and about 10%. The blue laser source of the present disclosure advantageously operates at a much greater efficiency. In particular, laser diodes are much more energy efficient than CO2 laser sources.[000248] The laser source may be configured to provide continuous wave blue radiation.[000249] It has been found that some materials are less likely to be damaged by continuous wave blue radiation compared to a pulsed radiation. For example, packaging foil may comprise an aluminium layer which may be very easily damaged by pulsed laser radiation. However, it has been found that continuous wave blue radiation is less likely to damage the aluminium layer.[000250] A rise time of the laser source may be about 30 ps or less.[000251] The rise time of the laser source may be about 25 ps or less.[000252] The rise time of the laser source may be about 20 ps or less.[000253] The rise time of the laser source may be about 15 ps or less.[000254] The rise time of the laser source may be about 12 ps.[000255] CO2 laser sources have a rise time of about 35 ps or more, e.g. up to about 100 ps, which is significantly longer than the rise time of the laser source of the present disclosure. Longer rise times are associated with more frequent marking errors due to, for example, burning the product and / or fading at the beginning and / or end of individual marks formed on the product. Reduced rise times advantageously avoid or reduce the frequency of said marking errors. In particular, laser diodes have faster rise times than CO2 laser sources.[000256] A fall time of the laser source may be about 60 ps or less.[000257] The fall time of the laser source may be about 50 ps or less.[000258] The fall time of the laser source may be about 30 ps or less.[000259] The fall time of the laser source may be about 15 ps or less.[000260] The fall time of the laser source may be about 10 ps or less.[000261] The fall time of the laser source may be about 8 ps or less.[000262] The fall time of the laser source may be about 5 ps or less.[000263] The fall time of the laser source may be about 0 ps.[000264] CO2 laser sources have a fall time of about 68 ps or more, e.g. up to about 84 ps, which is significantly longer than the fall time of the laser source of the present disclosure. Longer fall times are associated with more frequent marking errors due to, for example, burning the product and / or fading at the beginning and / or end of individual marks formed on the product. Reduced fall times advantageously avoid or reduce the frequency of said marking errors. In particular, laser diodes have faster fall times than CO2 laser sources.[000265] An end user of a CO2 based laser marking system may need to introduce delays such as, for example, adjusting a position of the steering mirrors in the marking head, between switching the CO2 laser source on and off to account for the relative large rise and / or fall times and thereby avoid or reduce the likelihood of marking errors. The laser source configured to generate blue radiation of the present disclosure does not suffer this drawback, thereby providing a less complex and more user friendly laser marking system that does not require the introduction of said delays.[000266] The laser source may be configured to output blue radiation having an annular beam profile.[000267] The laser source may be configured to generate TEMoo mode blue radiation.[000268] The laser source may be configured to generate multimode blue radiation.[000269] The laser source may be configured to generate single mode blue radiation.[000270] According to a tenth aspect of the present disclosure, there is provided a method of generating blue radiation comprising optically coupling blue radiation generated by a plurality of laser diodes to an optical fiber.[000271] Collecting the blue radiation may comprise incoherent polarization beam combining.[000272] Collecting the blue radiation may comprise spatial beam combining. Spatial beam combining may comprise arranging a plurality of mirrors with respect to a plurality of laser diodes. Each laser diode may have its own associated mirror configured to reflect the blue radiation emitted by the laser diode onto a common propagation path. The laser diodes and mirrors may be arranged to form a plurality of rows. The mirrors of each row may be slightly offset from each other such that blue radiation reflected by one of the mirrors is not blocked by a different mirror in the row. Each mirror may be adjustable such that each beam reflected from each mirror has substantially the same angular propagation direction. As such, all blue radiation beams generated by the plurality of laser diodes propagate along a common path having substantially the same propagation angle, and so may be considered to be spatially combined. Collecting the blue radiation may comprise wavelength beam combining.[000273] The method may comprise adding or removing at least one of the plurality of laser diodes to adjust a power of the laser source.[000274] The method may comprise operating the plurality of laser diodes below a maximum power rating of the plurality of laser diodes.[000275] The method may comprise generating blue radiation having a power within the inclusive range of about 1 W to about 200 W.[000276] The method may comprise generating blue radiation having a power that varies by 3% or less once a predetermined power and temperature are reached.[000277] The method may comprise generating blue radiation having a power that varies by 2% or less once a predetermined power and temperature are reached.[000278] The method may comprise generating blue radiation having a power that varies by 1% or less once a predetermined power and temperature are reached.[000279] The predetermined power may comprise a predetermined power range. The operating temperature may comprise an operating temperature range.[000280] The method may comprise generating continuous wave blue radiation. [000281] A rise time of the plurality of laser diodes may be about 30 ps or less. [000282] A fall time of the plurality of laser diodes may be about 60 ps or less.[000283] According to an eleventh aspect of the present disclosure, there is provided a method of manufacturing a laser source comprising optically coupling an optical fiber to a plurality of laser diodes configured to generate blue radiation.[000284] It will be appreciated that features described in the context of one aspect of the invention may be combined with features described in the context of another aspect of the invention. Any of the above aspects may be combined in any way.BRIEF DESCRIPTION OF THE DRAWINGS[000285] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labelled in every drawing. Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:Fig. 1 schematically depicts a laser marking system in accordance with the present disclosure.Fig. 2 schematically depicts an example coupling system in accordance with the present disclosure.Fig. 3 schematically depicts an internal view of a marking head in accordance with the present disclosure.Fig. 4 schematically depicts an electromagnetic radiation steering mechanism according to an embodiment of the present disclosure.Fig. 5A schematically depicts a cross-sectional view from the side of the marking head of Fig. 3.Fig. 5B schematically depicts a first alternative optical arrangement within the marking head according to an embodiment of the present disclosure.Fig. 5C schematically depicts a second alternative optical arrangement within the marking head according to an embodiment of the present disclosure.Fig. 6 schematically depicts a ray diagram of the blue radiation interacting with the first and second lenses of the marking head of Figs. 3 and 5A.Fig. 7A shows a beam profile of blue radiation generated by a free space laser source. Fig. 7B shows a beam profile of blue radiation generated by a laser source comprising an optical fiber in accordance with the present disclosure.Fig. 8 depicts a view of internal components of a laser source in accordance with the present disclosure.DETAILED DESCRIPTION[000286] Aspects and embodiments disclosed herein are not limited to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. Aspects and embodiments disclosed herein are capable of being practiced or of being carried out in various ways.[000287] Laser marking systems may be utilized in production lines for marking various types of articles. Laser marking systems may be utilized to imprint bar codes, unique identifying marks, expiration dates, or other information on items passing through a production line.[000288] Fig. 1 schematically depicts a laser marking system 100 in accordance with the present disclosure. The laser marking system 100 comprises a laser source 110 configured to generate blue radiation 115. The blue radiation 115 may comprise wavelengths of about 400 nm or more. The blue radiation 115 may comprise wavelengths of about 470 nm or less. The laser marking system 100 comprises a marking head 120 configured to project the blue radiation 115 on to a product 130 that is to be marked by the laser marking system 100. The laser marking system 100 comprises an optical fiber 140 configured to transmit the blue radiation 115 from the laser source 110 to the marking head 120.[000289] The optical fiber 140 may be a solid core optical fiber. The solid core optical fiber may comprise fused silica. The solid core optical fiber may have a core diameter of about 200 pm or less. The solid core optical fiber may have a core diameter of about 105 pm or less. The solid core optical fiber may have a core diameter of about 50 pm or less. The solid core optical fiber may have a core diameter of about 5 pm. Alternatively, the optical fiber 140 may be a hollow core optical fiber. The hollow core optical fiber may comprise fused silica. The hollow core optical fiber may have a core diameter of about 500 pm or less. The hollow core optical fiber may have a core diameter of about 100 pm or less. The core of the hollow core optical fiber may comprise a gas such as, for example, air or an inert gas such as argon, krypton, xenon, etc. Alternatively, the core of the hollow core fiber may comprise a vacuum. The optical fiber 140 may have a numerical aperture of about 0.1 or more. The optical fiber 140 may have a numerical aperture of about 0.5 or less. The optical fiber 140 may have a numerical aperture of about 0.22. A length of the optical fiber 140 may be about 15 m or less. The length of the optical fiber 140 may be, for example, about 10.75 m.[000290] The laser marking system 100 may comprise a coupling system configured to improve an optical coupling between the optical fiber 140 and an optical component of the laser marking system 100, such as the laser source 110 and / or the marking head 120. Fig. 2 schematically depicts an example coupling system 200 in accordance with the present disclosure. The coupling system 200 comprises first and second adjustable optical elements 215, 225 which, in the example of Fig. 2, comprise first and second rotatable reflectors. The coupling system 200 further comprises a first detector 230 configured to detect a position of the blue radiation 115 relative to the second adjustable optical element 225. The coupling system 200 further comprises a second detector 240 configured to detect a position of the blue radiation 115 relative to an input of the optical fiber 140. The first and second detectors 230, 240 may be configured to detect angular and / or translational positions of the blue radiation 115 relative to the second adjustable optical element 225 and the input of the optical fiber 140. A coupling lens 250 may be provided to capture the blue radiation 115 reflected from the second rotatable reflector 225 and focus the blue radiation towards a beam sampler 260. The beam sampler 260 comprises first and second optical flats 262, 264. The first optical flat 262 is configured to direct a portion of the blue radiation 115 to the second detector 240. A remaining portion of the blue radiation 115 may transmit through the first optical flat 262 and be incident upon the second optical flat 264. The second optical flat 264 is configured to compensate for refraction effects caused by the blue radiation 115 transmitting through the first optical flat 262. That is, the blue radiation 115 transmits through the second optical flat 264 towards the input of the optical fiber 140 and the second optical flat 264 refracts the blue radiation 115 to account for the refraction caused by the first optical flat 262. The second detector 240 is configured to detect an angular and / or translational position of the blue radiation 115 with respect to the input of the optical fiber 140 and / or an optical axis of the laser marking system. The first and / or second detectors 230, 240 may comprise a quadrant detector configured to provide positional information of the blue radiation 115, e.g. in the form of Cartesian coordinates.[000291] The coupling system 200 further comprises a controller 270 configured to receive signals from the first and second detectors 230, 240 and use the signals to control rotational positions of the first and second rotatable reflectors 215, 225 to thereby align the blue radiation 115 with the optical fiber 140 and / or an optical axis of the laser marking system. In the example of Fig. 2, the first and second rotatable reflectors 215, 225 have been rotated by the controller 270 in at least partial dependence on the signals received from the first detector 230 and the second detector 240. The first and secondrotatable reflectors 215, 225 have been rotated such that the blue radiation 115 is aligned with the optical fiber 140 and an optical axis of the laser marking system. The coupling system 200 may form part of the laser source 110. The coupling system 110 may form part of a housing that is separate from the marking head 120 by the optical fiber 140.[000292] The laser marking system 100 may comprise one or more coupling lenses 250 for optically coupling the optical fiber 140 to one or more other optical elements of the laser marking system 100, such as the laser source 110 and / or the marking head 120. An optimum ratio of a focal length to a diameter of an entrance pupil (i.e. an optimum F#) of the coupling lens 250 for coupling into the optical fiber 140 may be selected in at least partial dependence on the following equation:where Dcoreis the core diameter of the optical fiber 140, and A is the wavelength of the blue radiation. In practice, if the F# of the coupling lens 250 is less than F#Optthen more optical power may be coupled into higher order modes within the optical fiber 140 and thereby be attenuated. In practice, if the F# of the coupling lens 250 is less than F#Optthen the optical power may be clipped at an entrance to the optical fiber 140, which may in turn result in heating and possible thermal damage caused to the entrance of the optical fiber 140. As such, the F# of the coupling lens 250 may preferably be within the inclusive range of -5% and 2% of F#Opt.[000293] The F# of the coupling lens 250 may be selected in at least partial dependence on properties of the laser beam (e.g. a wavelength of the blue radiation 115) that is to be transmitted and / or a geometry of the optical fiber 140 itself. A ratio of a focal length of a coupling lens 250 located between the laser source 110 and the optical fiber 140 to a diameter of an entrance pupil of the optical fiber 140 may at least partially depend on a core diameter of the optical fiber 140.[000294] An end (not shown) of the optical fiber 140 may be tapered to improve a coupling efficiency of the optical fiber 140 with the laser source 110 and / or the marking head 120, thereby improving an efficiency of the laser marking system 100. The optical fiber 140 may comprise an end cap, e.g. a core-less end cap, (not shown) configured to improve an optical coupling between the optical fiber 140 and the laser source 110 and / or marking head 120 and / or to reduce a risk of damage to the optical fiber 140.[000295] The coupling system 200 may be configured to adjust an angle of incidence and / or a relative positioning between the blue radiation 115 emitted by the laser source 110 and an input of the optical fiber 140 to improve a coupling efficiency of the optical fiber 140. For example, the first and / or second rotatable reflector 215, 225 may berotated by the controller 270 to adjust the angle of incidence between the blue radiation 115 and the optical fiber 140. A beam profile of the blue radiation 115 in the optical fiber 140 and / or in the marking head 120 and / or in a marking spot 150 on the product 130 may be changed by adjusting the angle of incidence between the blue radiation 115 emitted by the laser source 110 and the input of the optical fiber 140. The coupling lens 250 may be configured to adjust a focus of the blue radiation 115 emitted by the laser source 110 before entering the input of the optical fiber 140 to improve a coupling efficiency of the optical fiber 140.[000296] The laser source 110 may comprise one or more laser diodes configured to generate the blue radiation 115. The laser source 110 may be configured such that a number of the laser diodes present in the laser source 110 is changeable. By increasing the number of laser diodes present in the laser source 110, a total output power of the laser source 100 may be increased. By decreasing the number of laser diodes present in the laser source 110, a total output power of the laser source 100 may be decreased. For example, a 10 W laser source may include three laser diodes, whereas a 30 W laser source may include eight laser diodes. A laser diode capacity of the laser source 110 may be selected in accordance with a maximum laser power desired by a user during manufacture of the laser source 110. Each of the multiple laser diodes may be optically coupled to the optical fiber 140 such that the optical fiber 140 receives multiple beams of blue radiation 115. Spatial beam combining and / or wavelength beam combining and / or polarization beam combining may be used to couple a plurality of blue laser beams generated by a plurality of laser diodes into the optical fiber 140. The plurality of laser diodes in the laser source 110 may be configured to operate below a maximum power rating of the plurality of laser diodes. This advantageously prolongs an operational lifetime of the laser diodes whilst the number of laser diodes present can be selected to reach a desired power level for a given laser marking application (e.g. to reach a desired marking speed).[000297] The laser marking system 100 may be configured to provide blue radiation having a power of about 1 Wor more. The laser marking system 100 may be configured to provide blue radiation having a power of about 200 W or less. The laser marking system 100 may be configured to provide blue radiation having a power of, for example, about 30 W.[000298] The laser marking system 100 may be configured to operate at a marking speed at a marking speed of about 1 mm s-1or more. The laser marking system 100 may be configured to operate at a marking speed of about 20000 mm s-1or less.[000299] The marking head 120 may be configured to project the blue radiation 115 such that the blue radiation 115 has a focal spot 150 diameter of about 10 pm or more. The marking head 120 may be configured to project the blue radiation 115 such that the blue radiation 115 has a focal spot 150 diameter of about 1000 pm or less. The marking head 120 may be configured to project the blue radiation 115 such that the blue radiation 115 has a focal spot 150 diameter of about 200 pm or more. The marking head 120 may be configured to project the blue radiation 115 such that the blue radiation 115 has a focal spot 150 diameter of about 550 pm or less. Focal spot 150 diameter may be understood as a beam diameter of the blue radiation 115 at or proximate a focal plane of the marking head 120. Focal spot 150 diameter may be understood as a beam diameter of the blue radiation 115 proximate a working distance 160 of the marking head 120. Focal spot 150 diameter may be understood as a beam diameter of the blue radiation 115 within a focal depth range 170 of the laser marking system 100, and may therefore encompass a range of values. Focal spot 150 diameter may be understood as a smallest beam diameter of the blue radiation 115.[000300] The laser marking system 100 may be configured to have a focal depth range 170 of about 4 mm or more. The laser marking system 100 may be configured to have a focal depth range 170 of about 35 mm or less. The laser marking system 100 may be configured to have a focal depth range 170 of about 40 mm or less. Focal depth range 170 may be understood as a range of distances between the marking head 120 and the product 130 across which the blue radiation 115 is in focus such that a mark may be formed as desired on the product 130. A diffractive optical element (not shown) may be incorporated into the laser marking system 100 to increase a focal depth range 170 of the laser marking system 100. The diffractive optical element may be transmissive or reflective. The diffractive optical element may comprise a plurality of features comprising different heights and / or materials configured to introduce different phase shifts to the blue radiation. The diffractive optical element may take the form of a sheet or foil that is applied to one of the mirrors or lenses of the laser marking system. The diffractive optical element may be configured to output blue radiation having a Bessel beam profile.[000301] The marking head 120 may be configured to operate at a working distance 160 of about 5 mm or more. The marking head 120 may be configured to operate at a working distance 160 of about 1000 mm or less. The working distance 160 of the marking head 120 may be about 18 mm or more. The working distance 160 of the marking head 120 may be about 192 mm or less. The working distance 160 of the marking head 120 may be about 140 mm or less. The working distance 160 of themarking head 120 may be understood as a distance between an optical output of the marking head 120 (e.g. a window through which the blue radiation 115 exits the marking head 120) and a marking plane at which the blue radiation 115 is in focus. The working distance 160 of the marking head 120 may be understood as a distance between a reference point on the marking head 120 or optic to the focal point of the laser marking system 100. The laser marking system 100 may have a plurality of working distances which form a working distance range 170 for marking products 130 at multiple working distances 160 or z positions within the working distance range 170.[000302] Fig. 3 schematically depicts an internal view of a marking head in accordance with the present disclosure. The marking head 120 comprises a collimator 180 configured to receive the blue radiation 115 transmitted to the marking head 120 by the optical fiber 140. The collimator 180 may be configured to provide a beam of blue radiation 115 having substantially parallel rays. The marking head 120 further comprises a first lens 310 configured to receive the blue radiation 115 output by the collimator 180 and expand the blue radiation 115. The marking head 120 comprises a folding mirror 315 configured to receive the expanded blue radiation 115 from the first lens 310 and direct the expanded blue radiation to a second lens 320. The second lens 320 is configured to receive the blue radiation 115 expanded by the first lens 310 and focus the blue radiation 115. At least one of the first and second lenses 310, 320 may comprise Suprasil 2A. The marking head 120 further comprises an electromagnetic radiation steering mechanism 100A, 100B, a, b configured to steer the blue radiation 115 to address a specific location within a two-dimensional field of view 330. In the example of Fig. 3, the electromagnetic radiation steering mechanism 100A, 100B, a, b receives blue radiation 115 that has been focused by the second lens 320.[000303] FIG. 4 shows an electromagnetic radiation steering mechanism according to an embodiment of the present disclosure. The electromagnetic radiation steering mechanism comprises a first optical element 100A having an associated first actuator A configured to rotate the first optical element 100A about a first rotational axis 410 to change a first coordinate of a first steering axis in the two-dimensional field of view. The electromagnetic radiation steering mechanism further comprises a second optical element 100B having an associated second actuator B configured to rotate the second optical element 100B about a second rotational axis 420 to change a second coordinate of a second steering axis in the two-dimensional field of view. The first actuator A and / or the second actuator B may comprise a galvanometer motor. In the example of FIG. 4, the first optical element 100A is adjacent the second optical element 100B. In theexample of FIG. 4, the first optical element 100A is offset from the second optical element 100B along an axis that is substantially parallel to the first and second rotational axes 410, 420. In the example of FIG. 4, the first optical element 100A comprises a first reflective surface configured to receive and reflect blue radiation 115 and the second optical element 100B comprises a second reflective surface configured to receive and reflect the blue radiation 115. In the example of FIG. 4, the first rotational axis 410 and the first reflective surface are substantially parallel, and the second rotational axis 420 and the second reflective surface are substantially parallel.[000304] The electromagnetic radiation steering mechanism further comprises an electromagnetic radiation manipulator “a”, “b” optically disposed between the first and second optical elements 100A, 100B. The first optical element 100A is configured to receive blue radiation 115 and direct the blue radiation 115 to the electromagnetic radiation manipulator “a”, “b”. The electromagnetic radiation manipulator “a”, “b” is configured to direct the blue radiation 115 to the second optical element 100B. The second optical element 100B may be configured to direct the blue radiation 115 to an optical output of the electromagnetic radiation steering mechanism.[000305] In the example of FIG. 4, the electromagnetic radiation manipulator comprises a first mirror “a” and a second mirror “b”. The first mirror “a” is configured to receive the blue radiation 115 after the blue radiation 115 has interacted with the first optical element 100A and direct the blue radiation 115 to the second mirror “b”. The second mirror “b” is configured to receive the blue radiation 115 after the blue radiation 115 has interacted with the first mirror “a” and direct the blue radiation 115 to the second optical element 100B. The first mirror “a” and the second mirror “b” are fixed with respect to each other.[000306] The first mirror “a” is arranged so as to apply about a 90° change in a propagation direction of the blue radiation 115. To achieve this, the first mirror “a” may be optically disposed at a 45° angle with respect to incident blue radiation 115. The second mirror “b” is arranged so as to apply about a 90° change in a propagation direction of the blue radiation 115. To achieve this, the second mirror “b” may be optically disposed at a 45° angle with respect to incident blue radiation 115. These changes in the propagation direction of the blue radiation 115 enable two orthogonal degrees of freedom for the beam deflection.[000307] A first angle is defined between the first and second rotational axes 410, 420 and a second angle is defined between the first and second steering axes. The electromagnetic radiation manipulator “a”, “b” is configured to introduce a differencebetween the first angle and the second angle. In the example of FIG. 4, the first rotational axis 410 and the second rotational axis 420 are non-orthogonal. In the example of FIG. 4, the first rotational axis 410 and the second rotational axis 420 are substantially parallel. In the example of FIG. 4, the first steering axis and the second steering axis are substantially orthogonal. That is, in the example of FIG. 4, the electromagnetic radiation manipulator “a”, “b” is configured to introduce a difference of about 90° between the first angle and the second angle.[000308] Fig. 5A schematically depicts a cross-sectional view from the side of the marking head of Fig. 3. The collimator 180 may be configured to condition the blue radiation 115 such that the collimator 180 outputs blue radiation 115 having a collimated beam diameter 510 of about 0.1 mm or more. The collimator 180 may be configured to condition the blue radiation 115 such that the collimator 180 outputs blue radiation 115 having a collimated beam diameter 510 of about 15 mm or less. The collimator 180 may be configured to condition the blue radiation 115 such that the collimator 180 outputs blue radiation 115 having a collimated beam diameter 510 of about 5 mm or less. The collimator 180 may be configured to condition the blue radiation 115 such that the collimator 180 outputs blue radiation 115 having a collimated beam diameter 510 of about 2.5 mm.[000309] The first lens 310 may have a focal length of about -5 mm or less. The first lens 310 may have a focal length of about -150 mm or more. The first lens 310 may have a focal length of about -24 mm. The first lens 310 may have a focal length of about -13 mm. The first lens 310 may be configured to expand the blue radiation 115 such that the blue radiation 115 has an expanded beam diameter 520 (also shown in Fig. 6) of about 0.5 mm or more at the second lens 320 (which is only partly visible in Fig. 5A). The first lens 310 may be configured to expand the blue radiation 115 such that the blue radiation 115 has an expanded beam diameter 520 of about 50 mm or less at the second lens 320. The first lens 310 may be configured to expand the blue radiation 115 such that the blue radiation 115 has an expanded beam diameter 520 of about 8 mm at the second lens 320.[000310] Fig. 6 schematically depicts a ray diagram of the blue radiation interacting with the first and second lenses of the marking head of Figs. 3 and 5A. The first lens 310 may have a centre thickness 610 of about 0.5 mm or more. The first lens 310 may have a centre thickness 610 of about 10 mm or less. The first lens 310 may have a centre thickness 610 of about 2 mm.[000311] The first lens 310 may have an edge thickness 620 of about 1 mm or more. The first lens 310 may have an edge thickness 620 of about 10 mm or less. The first lens 310 may have an edge thickness 620 of about 3.5 mm.[000312] Referring again to Fig. 5A, a propagation distance 530 between the collimator 180 and the first lens 310 may be about 1 mm or more. The propagation distance 530 between the collimator 180 and the first lens 310 may be about 100 mm or less. The propagation distance 530 between the collimator 180 and the first lens 310 may be about 4 mm.[000313] The second lens 320 may have a focal length of about 10 mm or more. The second lens 320 may have a focal length of about 1000 mm or less. The second lens 320 may have a focal length of about 27.5 mm or more. The second lens may have a focal length of about 38.23 mm or less. The second lens 320 may have a focal length of about 33.2 mm or less.[000314] Referring again to Fig. 6, the second lens 320 may have a centre thickness 630 of about 0.5 mm or more. The second lens 320 may have a centre thickness 630 of about 15 mm or less. The second lens 320 may have a centre thickness 630 of about 3 mm.[000315] The second lens 320 may have an edge thickness 640 of about 0.1 mm or more. The second lens 320 may have an edge thickness 640 of about 15 mm or less. The second lens 320 may have an edge thickness 640 of about 3.0 mm.[000316] A propagation distance 650, 660 between the first lens 310 and the second lens 320 may be about 5 mm or more. The propagation distance between the first lens 310 and the second lens 320 may be about 150 mm or less. The propagation distance 650, 660 between the first lens 310 and the second lens 320 may be about 23.8 mm. The propagation distance 650, 660 between the first lens 310 and the second lens 320 may correspond to a length of an optical axis of the marking head between the first lens 310 and the second lens 320.[000317] Referring again to Fig. 5A a propagation distance between the second lens 320 and the focal spot 150 of the marking head 120 may be about 10 mm or more. The propagation distance between the second lens 320 and the focal spot 150 of the marking head 120 may be about 1000 mm or less. The propagation distance between the second lens 320 and the focal spot 150 of the marking head 120 may be about 88 mm or more. The propagation distance between the second lens 320 and the focal spot 150 of the marking head 120 may be about 192 mm or less.[000318] In the examples of Figs. 3, 5A and 6, the marking head 120 comprises a folding mirror 315 located between the first lens 310 and the second lens 320. Referring again to Fig. 6, a distance 650 between the folding mirror 315 and the first lens 310 may be about 3 mm or more. The distance 650 between the folding mirror 315 and the first lens 310 may be about 150 mm or less. The distance 650 between the folding mirror 315 and the first lens 310 may be about 21.6 mm.[000319] A distance 660 between the folding mirror 315 and the second lens 320 may be about 3 mm or more. The distance 660 between the folding mirror 315 and the second lens 320 may be about 150 mm or less. The distance 660 between the folding mirror 315 and the second lens 320 may be about 5.8 mm.[000320] Alternative optical configurations within the marking head 120 may be used. For example, Fig. 5B schematically depicts a first alternative optical arrangement within the marking head according to an embodiment of the present disclosure. Compared to the marking head of Fig. 5A, the marking head 120 of Fig. 5B does not include the collimator or the first lens. The lack of the first lens is represented by the first lens being struck through in Fig. 5B. Instead, the marking head 120 comprises a focusing lens 320 (i.e. similar to the second lens of Fig. 5A) configured to receive expanding blue radiation 115 emitted by the optical fiber 140. The blue radiation 115 emitted by the optical fiber 140 will naturally expand (i.e. a beam diameter of the blue radiation 115 will increase as the blue radiation 115 propagates) upon exiting the optical fiber 140. By setting a propagation distance 540 between the output of the optical fiber 140 and the focusing lens 320, the blue radiation 115 may expand to a desired beam diameter before being focussed by the focusing lens 320 to a desired focal spot size on the product to be marked. The propagation distance 540 between an output of the optical fiber 140 and the focusing lens 320 may be such that the blue radiation 115 has a beam diameter 520 of about 0.5 mm or more at the focusing lens 320. The propagation distance 540 between an output of the optical fiber 140 and the focusing lens 320 may be such that the blue radiation 115 has a beam diameter 520 of about 50 mm or less at the focusing lens 320. The propagation distance 540 between the output of the optical fiber 140 and the focussing lens 320 may be such that the blue radiation 115 has a beam diameter 520 of about 8 mm at the focussing lens 320.[000321] Fig. 5C schematically depicts a second alternative optical arrangement within the marking head according to an embodiment of the present disclosure. Compared to the marking head of Fig. 5A, the marking head 120 of Fig. 5C does not include the first lens. The lack of the first lens is represented by the first lens being struck through in Fig.5C. Instead, the marking head 120 of Fig. 5C includes an alternative collimator 185 comprising a final lens 187 configured to expand the blue radiation 115. The focusing lens 320 of the marking head 120 (i.e. similar to the second lens of Fig. 5A) is configured to receive the blue radiation 115 expanded by the final lens 187 and focus the blue radiation 115. A focal length of the final lens 187 and a propagation distance 550 between the final lens 187 and the focusing lens 320 may be such that the blue radiation 115 has a beam diameter 520 about 0.5 mm or more at the focussing lens 320. The focal length of the final lens 187 and the propagation distance 550 between the final lens 187 and the focusing lens 320 may be such that the blue radiation 115 has a beam diameter 520 of about 50 mm or less at the focusing lens 320.[000322] In general, for embodiments in which a more divergent beam (i.e. a less collimated beam) is incident upon the focusing lens 320, smaller focal lengths may be selected for the focusing lens 320. In general, for embodiments in which a less divergent beam (i.e. a more collimated beam) is incident upon the focusing lens 320, greater focal lengths may be selected for the focusing lens 320.[000323] Referring again to Fig. 1 , the laser marking system 100 may comprise a housing 190 configured to house the laser source 110. The optical fiber 140 connects the housing 190 to the marking head 120 such that blue radiation generated in the housing 190 is transmitted through the optical fiber 140 before reaching the marking head 120. Locating the laser source 110 outside of the marking head 120 advantageously allows for a reduction in the size of the marking head 120 for easier integration into production lines. The housing 190 may comprise a cooling system 195 configured to cool the laser source 110. The cooling system 195 may, for example, comprise one or more of a fluid cooling system (e.g. comprise one or more conduits configured to convey a cooling fluid such as, for example, water), cooling fins configured to dissipate heat, cooling fans configured to generate a convection current to cool the laser source 110, etc. Cooling systems are typically bulky components. Locating the cooling system 195 in the housing 190 separate from the marking head 120 advantageously allows for a more compact marking head 120 that can be more easily integrated into production lines.[000324] The marking head 120 may be configured to project the blue radiation 115 towards the product 130 to be marked in a direction that is substantially parallel with a length of the marking head 120, e.g. as shown in the examples of Figs. 5A-C. Alternatively, the marking head 120 may be configured to project the blue radiation 115towards the product 130 to be marked in a direction that is substantially perpendicular to a length of the marking head 120, e.g. as shown in the examples of Figs. 1 and 3.[000325] Fig. 7A shows a beam profile of blue radiation generated by a free space laser source. A free space laser source involves the use of multiple laser diodes without sending the output beam of each laser diode through an optical fiber. Aligning the output beam of each laser diode in free space is difficult and a beam quality of each laser diode varies leading to a generally poor beam profile. As can be seen from Fig. 7A, the free space laser beam profile is non-circular beam profile having an erratic energy distribution.[000326] Fig. 7B shows a beam profile of blue radiation generated by a laser source comprising an optical fiber in accordance with the present disclosure. Use of an optical fiber optically coupled to a plurality of laser diodes avoids free space operation, and thereby advantageously avoids the associated drawbacks of free space operation. As can be seen from Fig. 7B when compared to Fig. 7A, the optical fiber provides a substantially circular beam profile that can be used to mark in any direction. The optical fiber provides a less erratic, more homogenous beam power distribution which enables higher quality marking. The optical fiber may be configured to provide a shared route of transmission for multiple blue laser sources, such as multiple laser diodes, and thereby avoids the limited focal range associated with alignment of a plurality of lasers operating in free space. The optical fiber may be configured to mix the blue radiation output by the plurality of laser diodes into a single output beam that enjoys substantially uniform propagation. Referring again to Fig. 1 , the optical fiber 140 may be configured to produce a beam profile that is similar to or substantially the same as the beam profile shown in Fig. 7B.[000327] In the example of Fig. 7B, the laser marking system is configured to output blue radiation having a substantially annular beam profile. The laser marking system may comprise a beam shaping element (e.g. a diffractive optical element and / or an axicon) configured to change the beam profile received from the laser source to the annular beam profile. Alternatively or additionally, the optical fiber 140 may be configured to output blue radiation having a substantially annular beam profile. That is, during the transport through the optical fiber 140 the beam profile of the blue radiation emitted by the laser source is converted to an annular beam profile.[000328] It may be desirable to operate the laser marking system such that a relatively large beam spot is achieved at a relatively small working distance. Contrary to convention, it has been found that by using an optical fiber to transmit the blue radiation,a quality of the beam of blue radiation is reduced, which in turn enables a relatively large beam spot to be achieved at relatively small working distances, which has been found to be preferable for laser marking applications. For example, the beam spot may have a diameter within the inclusive range of about 100 pm to about 1000 pm at a working distance within the inclusive range of about 18 mm to about 5 mm.[000329] The optical fiber may be configured to output a laser beam having an M2factor of about 20 or more. The optical fiber may be configured to output a laser beam having an M2factor of about 40 or less. The optical fiber may be configured to output a laser beam having a beam parameter product of about 2.9 mm mrad or more. The optical fiber may be configured to output a laser beam having a beam parameter product of about 5.5 mm mrad or less.[000330] Referring again to Fig. 1 , the laser source 110 may be configured to generate blue radiation 115 having a power that varies by 3% or less once a predetermined power and operating temperature are reached. The predetermined power may be selected based on one or more of the mark that is to be formed, the material of the product 130 (e.g. a film), a desired marking speed, etc. The laser source 110 may be configured to generate blue radiation 115 having a power that varies by 2% or less once the predetermined power and operating temperature are reached. The laser source 110 may be configured to generate blue radiation 115 having a power that varies by 1% or less once the predetermined power and operating temperature are reached. The predetermined power may comprise a predetermined power range. The operating temperature may comprise an operating temperature range. A sensor (not shown) such as, for example, a thermopile sensor may be used to measure the power (and a variation of the power) of the blue radiation 115. A suitable sensor may, for example, be a F150A- BB-26 Broadband 150 W Fan-Cooled Thermopile Sensor with 26 mm Aperture available from Ophir Optronics Solutions Ltd.[000331] The laser source 110 may have an energy efficiency of about 15% or more. The laser source 110 may have an energy efficiency of about 20% or more. The laser source 110 may have an energy efficiency of about 25% or more. The laser source 110 may have an energy efficiency of about 30% or more. The energy efficiency of the laser source 110 may be referred to in the art as wall-plug efficiency. The energy efficiency of the laser source 110 may be determined by measuring the amount of electrical power drawn by the laser source 110 and comparing this to the laser power output by the laser source 110. For example, a 30 W laser power produced by drawing 150 W of electrical power results in a wall-plug efficiency of 20 %.[000332] The laser source may be configured to provide continuous wave blue radiation. It has been found that some materials are less likely to be damaged by continuous wave blue radiation compared to a pulsed radiation. For example, packaging foil may comprise an aluminium layer which may be very easily damaged by pulsed laser radiation. However, it has been found that continuous wave blue radiation is less likely to damage the aluminium layer.[000333] The laser source 110 may be configured to generate TEMoo mode blue radiation. It has been found that TEMoo mode blue radiation typically produces a relatively small focal spot, which can be advantageous in some laser marking applications. For example, for marking materials such as metals, a smaller focal spot may be required to generate enough intensity for fast marking speeds. The laser source 110 may be configured to generate multimode blue radiation. It has been found that multimode blue radiation typically produces a relatively large focal spot having a reduced beam quality relative to other modes, which can be advantageous in some laser marking applications. For example, for marking some consumer packaged goods (CPG) materials, such as films, a larger beam diameter may be required to improve a visibility of the mark (e.g. to reach a certain font size) and / or to reduce a risk of damaging the film. The laser source 110 may be configured to generate single mode blue radiation. It has been found that single mode beams, besides TEMoo, generate very uniform line marks due to a relatively even power distribution. For example, a single mode beam having an annular beam profile may advantageously provide improved beam power distribution for marking with greater uniformity.[000334] A rise time of a laser source may be understood as the time taken for the power of radiation generated by the laser source to increase from a lower predetermined value to a higher predetermined value. The lower predetermined value may be, for example, within the inclusive range of about 0% to about 10% of a maximum power of the laser source. The higher predetermined value may be, for example, within the inclusive range of about 90% to about 100% of the maximum power of the laser source. A rise time of the laser source 110 may be about 30 ps or less. The rise time of the laser source 110 may be about 25 ps or less. The rise time of the laser source 110 may be about 20 ps or less. The rise time of the laser source 110 may be about 15 ps or less. The rise time of the laser source 110 may be about 12 ps. Known CO2 laser sources have a rise time of about 35 ps or more, e.g. up to about 100 ps, which is significantly longer than the rise time of the laser source 110 of the present disclosure. Longer rise times are associated with more frequent marking errors due to, for example, burning theproduct, perforating a film and / or fading at the beginning and / or end of individual marks formed on the product. Reduced rise times advantageously avoid or reduce the frequency of said marking errors. In particular, laser diodes have faster rise times than CO2 laser sources.[000335] A fall time of a laser source may be understood as the time taken for the power of radiation generated by the laser source to decrease from a higher predetermined value to a lower predetermined value. The higher predetermined value may be, for example, within the inclusive range of about 90% to about 100% of a maximum power of the laser source. The lower predetermined value may be, for example, within the inclusive range of about 0% to about 10% of the maximum power of the laser source. A fall time of the laser source 110 of the present disclosure may be about 60 ps or less. The fall time of the laser source 110 may be about 50 ps or less. The fall time of the laser source 110 may be about 30 ps or less. The fall time of the laser source 110 may be about 15 ps or less. The fall time of the laser source 110 may be about 10 ps or less. The fall time of the laser source 110 may be about 8 ps or less. The fall time of the laser source 110 may be about 5 ps or less. The fall time of the laser source 110 may be about 0 ps. Known CO2 laser sources have a fall time of about 68 ps or more, e.g. up to about 84 ps, which is significantly longer than the fall time of the laser source 110 of the present disclosure. Longer fall times are associated with more frequent marking errors due to, for example, burning the product, perforating a film and / or fading at the beginning and / or end of individual marks formed on the product. Reduced fall times advantageously avoid or reduce the frequency of said marking errors. In particular, laser diodes have faster fall times than CO2 laser sources.[000336] An end user of a CO2 based laser marking system may need to introduce delays such as, for example, adjusting a position of the steering mirrors in the marking head, between switching the CO2 laser source on and off to account for the relative large rise and / or fall times and thereby avoid or reduce the likelihood of marking errors. The laser source 110 configured to generate blue radiation 115 of the present disclosure does not suffer this drawback, thereby providing a less complex and more user friendly laser source that does not require the introduction of said delays.[000337] The product 130 may be a film. That is, the laser marking system 100 may be configured to mark a film 130 The marking head may be configured to project the blue radiation 115 generated by the laser source 110 on to the film when the film is located at a working distance of the marking head. The laser marking system 100 may not includethe optical fiber 140. For example, the laser marking system may be operated in free space when marking the film 130.[000338] The film 130 may comprise at least one of a plastic, a metal, a textile, and a paper. The film 130 may comprise any combination of the plastic, the metal, the textile and the paper. The film 130 may comprise a plurality of layers. The plurality of layers may comprise individual layers of plastic and / or metal and / or textile and / or paper. The plurality of layers may comprise individual layers formed of different plastics. The plastic may comprise one or any combination of polyethylene, polypropylene, polystyrene, polyethylene Terephthalate, polyvinyl-chloride. The metal may comprise aluminium.[000339] The film 130 may have a thickness 135 of about 20 pm or more. The film 130 may have a thickness of about 50 pm or more. The film 130 may have a thickness of about 1000 pm or less. The film 130 may have a thickness of about 200 pm or less. [000340] The film 130 may be flexible.[000341] The laser marking system 100 may be configured such that the blue radiation induces ablation and / or a chemical reaction on the film 130. The chemical reaction may comprising using the blue radiation 115 to change a colour of the film 130. For example, the film 130 may comprise ink. The chemical reaction may change a colour of the ink. It has been found that whilst blue radiation 115 may not be strongly absorbed by many film 130 base materials, blue radiation 115 is strongly absorbed by ink within the film 150. This advantageously allows high quality marking through alteration of the ink whilst the base material is not damaged by the blue radiation 115.[000342] The laser marking system 100 may comprise a mode scrambler 197. In the example of Fig. 1 , the mode scrambler 197 is located in the housing 190. The mode scrambler 197 may be located elsewhere, e.g. in the laser source 110, the marking head 120 or along the optical fiber 140. The mode scrambler 197 is configured to mix the power of different modes in the optical fiber 140 so that a uniformity of a power distribution across all modes in the optical fiber 140 is improved. The mode scrambler 197 may comprise a mechanical device (not shown) configured to apply a controllable amount of pressure or mechanical stress on the optical fiber 140 and thereby bend the optical fiber 140 in a controllable manner. Introducing controlled bending of the optical fiber 140 may increase mode coupling among different modes, which may be referred to in the art as mode scrambling. A controller (not shown) may be used to adjust a pressure applied to the optical fiber 140 until a desired power distribution is achieved. The mode scrambler 197 may comprise a combination of a step-index fiber and a graded index fiber. For example, a graded index fiber may be located between two step-index fibers.A step-index fiber may be understood as a fiber comprising two different indices of refractions. A graded index fiber may be understood as a fiber comprising a gradually changing index of refraction. Refractive indices of the step-index and graded index fibers may be selected in at least partial dependence upon a numerical aperture of the optical fiber 140. For example, a numerical aperture of the optical fiber 140 may be within the inclusive range of about 0.1 to about 0.5, in which case a core refractive index of the mode scrambler 197 may be within the inclusive range of about 0.1 to about 1.45, and a cladding refractive index of the mode scrambler 197 may be within the inclusive range of about 0.5 to about 1 .37. The mode scrambler 197 may be configured to distribute the blue radiation 115 in the optical fiber 140 into a distribution of modes that experience increased stability across the length of the optical fiber 140. The mode scrambler 197 may act to improve a spatial energy homogeneity of the blue radiation 115, which in turn may improve a marking quality of the laser marking system 100.[000343] Fig. 8 depicts a view of internal components of a laser source in accordance with the present disclosure. The laser source 110 comprises a plurality of laser diodes 801-810 configured to generate blue radiation. In the example of Fig. 8, the laser source 110 comprises ten laser diodes 801-810. The laser source 110 may comprise a greater or lesser number of laser diodes 801-810 to generate a different output laser power as described above. The laser source 110 comprises an optical fiber 140 that is optically coupled to the plurality of laser diodes 801-810 and configured to collect the blue radiation generated by the plurality of laser diodes 801-810.[000344] The laser source 110 comprises a coupling system configured to optically couple the plurality of laser diodes 801-810 to the optical fiber 140. In the example of Fig. 8, the coupling system is a spatial beam combiner comprising a plurality of mirrors 811-820 associated with the plurality of laser diodes 801-810. In the example of Fig. 8, the laser diodes and mirrors are split between a first row 801-805, 811-815 and a second row 806-810, 816-820. The mirrors of each row 811-815, 816-820 are slightly offset from each other such that blue radiation reflected by one of the mirrors is not blocked by a different mirror. Each mirror of the first row 811-815 receives blue radiation from its respective laser diode 801-805 and reflects the blue radiation towards a folding mirror 825. Each mirror of the second row 816-820 receives blue radiation from its respective laser diode 806-810 and reflects the blue radiation towards a wave plate 830, e.g. a half wave plate, configured to change a polarization direction of the blue radiation generated by the second row of laser diodes 806-810. Each mirror may be adjustable such that each beam reflected from each mirror of a given row has substantially the same angularpropagation direction. Blue radiation transmitted by the wave plate 830 is incident upon a polarization beam combiner 840. Blue radiation reflected by the folding mirror 825 is incident upon the polarization beam combiner 840. Given the difference in polarization direction introduced by the wave plate 830, blue radiation generated by the first row of laser diodes 801-805 is reflected by the polarization beam combiner 840 whereas blue radiation generated by the second row of laser diodes 806-810 is transmitted by the polarization beam combiner 840 such that the blue radiation generated by all of the laser diodes 801-810 is combined into a single beam. The single combined beam is incident upon a coupling lens 250 (which may correspond to the coupling lens of Fig. 2). The coupling lens 250 is configured to adjust a focus of the blue radiation emitted by the plurality of laser diodes 801-810 before entering an input of the optical fiber 140 and thereby improving a coupling efficiency into the optical fiber 140. The optical fiber 140 transports the blue radiation 115 to the collimator 180 of the marking head.[000345] A method of marking the product according to the present disclosure may comprise generating blue radiation 115 (e.g. using the laser source 110 comprising one or more laser diodes). The method may comprise transmitting the blue 115 radiation through the optical fiber 140, e.g. a solid core optical fiber 140 having a core diameter of about of about 200 pm or less (e.g. about 50 pm or less). The method may comprise projecting the blue radiation 115 on to the product 130 (e.g. using the marking head 120 to project the blue radiation 115 on to a film 130).[000346] The method may comprise generating multimode blue radiation.[000347] The method may comprise projecting the blue radiation such that the blue radiation has a focal spot diameter of about 200 pm or more. The method may comprise projecting the blue radiation such that the blue radiation has a focal spot diameter of about 550 pm or less.[000348] The method may comprise using the optical fiber to output a laser beam having an M2factor of about 20 or more. The method may comprise using the optical fiber to output a laser beam having an M2factor of about 40 or less. The method may comprise using the optical fiber to output a laser beam having a beam parameter product of about 2.9 mm mrad or more. The method may comprise using the optical fiber to output a laser beam having a beam parameter product of about 5.5 mm mrad or less.[000349] The method may comprise using a plurality of laser diodes to generate the blue radiation. The method may comprise using the optical fiber to collect the blue radiation generated by the plurality of laser diodes.[000350] The method may comprise using spatial beam combining to combine the blue radiation generated by the plurality of laser diodes.[000351] The method may comprise using polarization beam combining to combine the blue radiation generated by the plurality of laser diodes.[000352] The method may comprise generating continuous wave blue radiation.[000353] A method of manufacturing a laser marking system 100 according to the present disclosure may comprise optically coupling a first end of the optical fiber 140 to the laser source 110 configured to generate the blue radiation 115. The method may comprise optically coupling a second end of the optical fiber 140 to the marking head 120 configured to project the blue radiation 115 on to the product 130.[000354] A method of generating the blue radiation 115 according to the present disclosure may comprise collecting the blue radiation 115 generated by a plurality of laser diodes (e.g. located within the laser source 110) using an optical fiber 140. Collecting the blue radiation 115 may comprise coherent polarization combining of the blue radiation 115 generated by different laser diodes within the laser source 110. Collecting the blue radiation 115 may alternatively or additionally comprise spatial beam combining and / or wavelength beam combining. The method may comprise adding or removing at least one of the plurality of laser diodes to / from the laser source 110 to adjust a power of the laser source 110. The method may comprise operating the plurality of laser diodes below a maximum power rating of the plurality of laser diodes. The method may comprise generating the blue radiation 115 such that the blue radiation 115 has a power of about 1 W or more. The method may comprise generating the blue radiation 115 such that the blue radiation 115 has a power of about 200 W or less. Adding or removing laser diodes may be used to adjust the power of the blue radiation 115. The method may comprise generating the blue radiation 115 such that the blue radiation 115 has a power that varies by 3% or less once a predetermined power and operating temperature are reached. The predetermined power may at least partially depend on the product 130 that is to be marked. The method may comprise generating continuous wave blue radiation 115. A rise time of the plurality of laser diodes may be about 30 ps or less. A fall time of the plurality of laser diodes may be about 60 ps or less.[000355] A method of manufacturing a laser source in accordance with the present disclosure may comprise connecting an optical fiber 140 to a plurality of laser diodes configured to generate the blue radiation 115.[000356] A method of retrofitting a production system in accordance with the present disclosure may comprise replacing a continuous inkjet marking system with the laser marking system 100.[000357] A method of marking a film in accordance with the present disclosure may comprise generating the blue radiation 115 (e.g. using a plurality of laser diodes optically coupled to each other using an optical fiber 140. The method may comprise projecting the blue radiation 115 on to the film 130 (e.g. using the marking head 120 and the optical components therein). The method may comprise inducing ablation and / or a chemical reaction on the film 130. The chemical reaction may comprise using the blue radiation 115 to change a colour of the film 130. The method may comprise inducing a colour change of the film 130.[000358] A method of manufacturing a laser marking system in accordance with the present disclosure may comprise optically coupling the laser source 110 configured to generate the blue radiation 115 to the marking head 120 configured to project the blue radiation 115 on to the film 130 when the film 130 is located at the working distance 160 from the marking head 120.[000359] Having thus described several aspects of at least one implementation, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the disclosure. The acts of methods disclosed herein may be performed in alternate orders than illustrated, and one or more acts may be omitted, substituted, or added. One or more features of any one example disclosed herein may be combined with or substituted for one or more features of any other example disclosed. Accordingly, the foregoing description and drawings are by way of example only.[000360] The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. As used herein, the term “plurality” refers to two or more items or components. As used herein, dimensions which are described as being “substantially” similar may be considered to be within about 25% of one another. The terms “comprising,” “including,” “carrying,” “having,” “containing,” and “involving,” whether in the written description or the claims and the like, are open-ended terms, i.e., to mean “including but not limited to.” Thus, the use of such terms is meant to encompass the items listed thereafter, and equivalents thereof, as well as additional items. Only the transitional phrases “consisting of” and “consisting essentially of,” are closed or semi-closed transitional phrases, respectively, with respect to the claims. Useof ordinal terms such as “first,” “second,” “third,” and the like in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.[000361] The laser marking system and laser source may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, and / or other types of optical components, or any combination thereof, for directing, shaping, and / or controlling the blue radiation.[000362] Where the context allows, embodiments of the present disclosure may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the present disclosure may also be implemented as instructions stored on a machine- readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read only memory (ROM); random access memory (RAM); magnetic storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g. carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc. and in doing that may cause actuators or other devices to interact with the physical world.[000363] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

Claims

CLAIMS:

1. A laser marking system for marking a product comprising: a laser source configured to generate blue radiation; a marking head configured to project the blue radiation on to the product; and, an optical fiber configured to transmit the blue radiation from the laser source to the marking head.

2. The laser marking system of claim 1 , wherein the laser marking system is configured to output multimode blue radiation.

3. The laser marking system of any preceding claim, wherein the laser source is configured to generate multimode blue radiation.

4. The laser marking system of any preceding claim, being configured to have a focal depth range of about 4 mm or more.

5. The laser marking system of any preceding claim, being configured to have a focal depth range of about 35 mm or less.

6. The laser marking system of any of claims 1 to 4, being configured to have a focal depth range of about 40 mm or less.

7. The laser marking system of any preceding claim, wherein the marking head is configured to project the blue radiation such that the blue radiation has a focal spot diameter of about 200 pm or more.

8. The laser marking system of claim any preceding claim, wherein the marking head is configured to project the blue radiation such that the blue radiation has a focal spot diameter of about 550 pm or less.

9. The laser marking system of any preceding claim, wherein a working distance of the marking head is about 18 mm or more.

10. The laser marking system any preceding claim, wherein a working distance of the marking head is about 192 mm or less.11 . The laser marking system of any of claims 1 to 9, wherein a working distance of the marking head is about 140 mm or less.

12. The laser marking system of any preceding claim, wherein the optical fiber is configured to output a laser beam having an M2factor of about 20 or more.

13. The laser marking system of any preceding claim, wherein the optical fiber is configured to output a laser beam having an M2factor of about 40 or less.

14. The laser marking system of any preceding claim, wherein the optical fiber is configured to output a laser beam having a beam parameter product of about 2.9 mm mrad or more.

15. The laser marking system of any preceding claim, wherein the optical fiber is configured to output a laser beam having a beam parameter product of about 5.5 mm mrad or less.

16. The laser marking system of any preceding claim, wherein the laser source comprises a plurality of laser diodes configured to generate the blue radiation, and wherein the optical fiber is coupled to the plurality of laser diodes and configured to collect the blue radiation generated by the plurality of laser diodes.

17. The laser marking system of any preceding claim, wherein the laser source comprises a coupling system configured to optically couple the plurality of laser diodes to the optical fiber.

18. The laser marking system of claim 17, wherein the coupling system comprises a coupling lens configured to adjust a focus of the blue radiation emitted by the plurality of laser diodes before entering an input of the optical fiber.

19. The laser marking system of claim 17 or claim 18, wherein the coupling system comprises a polarization beam combiner configured to combine blue radiation generated by the plurality of laser diodes.

20. The laser marking system of any of claims 17 to 19, wherein the coupling system comprises a spatial beam combiner configured to combine blue radiation generated by the plurality of laser diodes.

21. The laser marking system of any preceding claim, wherein the marking head comprises a collimator configured to receive the blue radiation transmitted to the marking head by the optical fiber.

22. The laser marking system of any preceding claim, wherein the laser source is configured to generate continuous wave blue radiation.

23. The laser marking system of any preceding claim, wherein the marking head comprises an electromagnetic radiation steering mechanism configured to steer the blue radiation to address a specific location within a two-dimensional field of view, the electromagnetic radiation steering mechanism comprising: a first optical element having an associated first actuator configured to rotate the first optical element about a first rotational axis to change a first coordinate of a first steering axis in the two-dimensional field of view; a second optical element having an associated second actuator configured to rotate the second optical element about a second rotational axis to change a second coordinate of a second steering axis in the two-dimensional field of view; and an electromagnetic radiation manipulator optically disposed between the first and second optical elements, wherein a first angle is defined between the first and second rotational axes; a second angle is defined between the first and second steering axes; and, the electromagnetic radiation manipulator is configured to introduce a difference between the first angle and the second angle.

24. The laser marking system of claim 23, wherein the first rotational axis and the second rotational axis are non-orthogonal.

25. The laser marking system of claim 23 or claim 24, wherein the first steering axis and the second steering axis are substantially orthogonal.

26. The laser marking system of any of claims 23 to 25, wherein the electromagnetic radiation manipulator comprises a first mirror and a second mirror that are fixed with respect to each other.

27. The laser marking system of any of claims 23 to 26, wherein at least one of the first actuator and second actuator comprises a galvanometer motor.

28. The laser marking system of any preceding claim comprising a housing configured to house the laser source, wherein the optical fiber connects the housing to the marking head.

29. A method of retrofitting a production system comprising a continuous inkjet marking system, the method comprising replacing the continuous inkjet marking system with the laser marking system of any preceding claim.

30. A method of marking a product comprising: generating blue radiation; transmitting the blue radiation through an optical fiber; and, projecting the blue radiation on to the product.

31. The method of claim 30, comprising generating multimode blue radiation.

32. The method of claim 30 or claim 31 , comprising projecting the blue radiation such that the blue radiation has a focal spot diameter of about 200 pm or more.

33. The method of any of claims 30 to 32, comprising projecting the blue radiation such that the blue radiation has a focal spot diameter of about 550 pm or less.

34. The method of any of claims 30 to 33, comprising using the optical fiber to output a laser beam having an M2factor of about 20 or more.

35. The method of any of claims 30 to 34, comprising using the optical fiber to output a laser beam having an M2factor of about 40 or less.

36. The method of any of claims 30 to 35, comprising using the optical fiber to output a laser beam having a beam parameter product of about 2.9 mm mrad or more.

37. The method of any of claims 30 to 36, comprising using the optical fiber to output a laser beam having a beam parameter product of about 5.5 mm mrad or less.

38. The method of any of claims 30 to 37, comprising: using a plurality of laser diodes to generate the blue radiation and, using the optical fiber to collect the blue radiation generated by the plurality of laser diodes.

39. The method of claim 38, comprising using spatial beam combining to combine the blue radiation generated by the plurality of laser diodes.

40. The method of claim 38 or claim 39, comprising using polarization beam combining to combine the blue radiation generated by the plurality of laser diodes.

41. The method of any of claims 30 to 40, comprising generating continuous wave blue radiation.

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