Light generating device for a microscope

Abstract

A light-generating device (204) for a microscope (202) includes: a first laser unit (206) having a fiber arrangement (220) composed of optical fibers (212, 216, 218), the fiber arrangement including a nonlinear optical fiber (218) configured to generate a supercontinuum laser; and at least one second laser unit (208) configured to generate an additional laser in a spectrum outside the supercontinuum laser. The second laser unit (208) includes a connecting fiber (222) connected to one of the optical fibers (212, 216, 218) of the fiber arrangement (220) of the first laser unit (206) to spatially combine the additional laser and the supercontinuum laser.

Description

Technical Field

[0001] The present invention relates to a light generating device and a microscope system including such a light generating device. Background Technology

[0002] Supercontinuum laser sources, also known as white light laser sources (WLLs), are widely used in laser scanning microscopes. These sources initially generate high-power pulsed laser light at near-infrared (NIR) wavelengths. The pulsed NIR laser light is then coupled into a nonlinear optical fiber, where nonlinear optical effects cause significant spectral broadening. Thus, the initial narrowband laser pulse is converted into a continuous broadband spectrum covering a wide wavelength range from NIR to blue-green or blue.

[0003] While high-end supercontinuum laser sources can achieve wavelengths as short as 440 nm, achieving even shorter wavelengths remains a challenge. Generating shorter wavelengths via supercontinuum processes requires higher pump power, which accelerates the degradation of nonlinear fibers and ultimately shortens the laser source's lifetime. However, from an application perspective, shorter wavelengths are highly favored in modern laser scanning microscopy, making their development a key focus in this field.

[0004] Conventional approaches often bridge the spectral gap between application requirements and existing supercontinuum laser technology by adding an additional laser source (e.g., a solid-state laser source) that provides the required, typically shorter wavelength. This additional laser source is then integrated into free space, either directly into the microscope or into a common light guide leading to the microscope. However, this method suffers from higher cost and increased instability due to the need for additional optical components in free-space beam routing. Summary of the Invention

[0005] The purpose of this invention is to provide a light generation device for a microscope system that can provide laser light over a wide wavelength range, while also featuring a compact design and a long service life.

[0006] The above-mentioned objectives are achieved by the subject matter of the independent claims. Further embodiments are defined by the dependent claims and the following description.

[0007] The light generating apparatus includes a first laser unit having a fiber arrangement composed of optical fibers, the optical fibers including nonlinear optical fibers configured to generate supercontinuum laser light. The light generating apparatus also includes at least one second laser unit configured to generate additional laser light in a spectrum outside the supercontinuum laser light. The second laser unit includes a connecting fiber connected to one of the optical fibers in the fiber arrangement of the first laser unit to spatially combine the additional laser light and the supercontinuum laser light.

[0008] Compared to conventional methods that aim to extend the wavelength range of a white laser source by influencing supercontinuum processes in nonlinear optical fibers (which require higher pump power and thus carry a higher risk of fiber degradation), the proposed solution avoids fiber degradation by keeping the first laser unit essentially unchanged. Instead, an additional second laser unit is used to extend the wavelength range beyond the spectral capacity of the first laser unit. Furthermore, by using connecting optical fibers, the light generation device essentially eliminates the need for free-space propagation to combine the laser emitted by the second laser unit with the supercontinuum light emitted by the first laser unit. This allows for a compact design of the laser generation device, as no dedicated optical components are required for free-space beam routing. Here, free-space propagation refers to the transmission of a laser beam guided by optical components such as lenses and mirrors in open space, rather than the laser beam being confined within a medium such as an optical fiber. In particular, when the laser beam is directly coupled into the optical fiber, even if there is typically a small gap between the laser unit and the fiber, this should not be considered free-space propagation in the sense of this disclosure.

[0009] According to one embodiment, the nonlinear optical fiber is composed of photonic crystal fiber. Photonic crystal fiber contains periodic microstructures, such as arrays of air holes capable of achieving customized dispersion characteristics and high optical nonlinearity. Another embodiment of the nonlinear optical fiber that can be used in the proposed light generation device is, for example, a tapered fiber with a significantly reduced core diameter to increase power density and enhance nonlinearity, or a specially designed glass fiber doped with materials such as germanium.

[0010] Typically, the additional laser generated by the second laser unit is unrelated to the generation of the supercontinuum laser. This means that the combination of the supercontinuum laser generated by the first laser unit and the additional laser generated by the second laser unit should be understood as a pure spatial superposition of light with different spectral components, without any interaction between these spectral components, and will not induce specific optical effects such as pumping that could significantly affect the generation of the supercontinuum laser.

[0011] According to one embodiment, a first laser unit includes a seed laser and a pump laser. The seed laser has a seed fiber configured to transmit the seed laser, and the pump laser has a pump fiber configured to transmit the pump laser. The fiber arrangement of the first laser unit includes a seed fiber, a pump fiber, and a nonlinear fiber. The nonlinear fiber is directly or indirectly coupled to the seed fiber and the pump fiber to generate supercontinuum laser based on the seed laser and the pump laser.

[0012] The seed laser can be constructed from a pulsed laser with low optical emission power. The laser pulse emitted from the seed laser is in the near-infrared (NIR) range, with a typical wavelength of 1064 nm. The pump laser can be a continuous-wave (CW) laser, which pumps the seed fiber or pump fiber, thereby amplifying the low-power pulse emitted by the seed laser. The amplified NIR laser pulse then enters a nonlinear fiber, where it generates supercontinuum laser light through nonlinear optical effects.

[0013] According to one embodiment, the connecting fiber of the second laser unit is connected to one of a seed fiber, a pump fiber, or a nonlinear fiber. Since the additional laser emitted by the second laser unit is substantially independent of the process of generating the supercontinuum laser emitted by the first laser unit, one of the fibers contained in the first laser unit can be selected to combine the additional laser with the supercontinuum laser, and the connecting fiber is connected to that fiber.

[0014] The fiber arrangement of the first laser unit includes an output fiber connected to the output end of the nonlinear optical fiber. A connecting fiber of the second laser unit is connected to this output fiber. Using the output fiber, which couples the light-generating device to the microscope, instead of directly connecting the nonlinear optical fiber to the microscope offers advantages in terms of flexibility.

[0015] According to one embodiment, the connecting fiber of the second laser unit is coupled to the fiber arrangement of the first laser unit via a splicing fiber connection. The fiber connection can be achieved using fusion splicing or mechanical splicing. During fusion splicing, the fiber end faces are precisely aligned and fused together using an electric arc. Mechanical splicing involves aligning and fixing the fiber end faces together using a fiber merging module. Mechanical splicing is preferred because it is less expensive than fusion splicing and only results in slightly higher, but still acceptable, insertion loss.

[0016] The second laser unit can be composed of a monolithic laser module with a connecting fiber permanently attached to it. Such a monolithic laser module with the fiber permanently attached to its output end is also called a pigtail laser. The permanently attached connecting fiber helps guide the emitted laser, improves beam stability, and makes the second laser unit easy to integrate into the light generation device. Furthermore, in terms of beam pointing, laser noise, power drift, and power fluctuation, this type of pigtail laser, using a fiber arrangement directly spliced ​​to the first laser unit, is a cost-effective and stable solution.

[0017] According to one embodiment, the light generating device includes a single housing in which a first laser unit and a second laser unit are jointly housed. The arrangement of the components of the light generating device within a single housing enables a compact design, and in particular, the power supply and cooling elements can be shared by the light generating device, the first laser unit, and / or the second laser unit.

[0018] The second laser unit can be configured to generate an additional laser with at least one single wavelength. As an example use case, it can be assumed that the supercontinuum wavelength of the first laser unit is limited to between 440 nm and 800 nm, while a specific application requires an additional laser with a wavelength of 405 nm. In this case, by employing a second laser unit, the additional wavelength of 405 nm can be conveniently combined with the supercontinuum. As another example, it can be assumed that the shortest wavelength of the aforementioned supercontinuum extends only to 480 nm, but an application requires both 405 nm and 440 nm wavelengths simultaneously. In this case, two independent additional units in the form of a second laser unit can be provided, outputting additional wavelengths of 440 nm and 405 nm respectively. Furthermore, it is also possible to provide only one additional laser unit to add two discrete wavelengths to the supercontinuum.

[0019] It goes without saying that this concept can be extended to more than two additional wavelengths. Furthermore, additional lasers located spectrally outside the supercontinuum laser can also be configured as a continuous wavelength range, rather than one or more independent wavelengths. Therefore, at least one second laser unit can include one or more line lasers, or lasers configured to emit additional lasers in a continuous spectrum.

[0020] The second laser unit can be configured to generate additional laser light with a wavelength shorter than the minimum wavelength of the supercontinuum laser. For example, the additional wavelength could be less than 470 nm or even less than 410 nm. As described above, conventional methods for increasing the spectral capacity of a white light laser source to extend the supercontinuum by one or more very short wavelengths require high pump power. This can lead to significant degradation of the nonlinear fiber. This embodiment reliably avoids fiber degradation by preventing excessive pump power.

[0021] The second laser unit may include a solid-state laser, and in particular a diode laser capable of achieving a compact design.

[0022] The second laser unit may include a pulsed laser. Using a pulsed laser allows the additional laser to be synchronized with a supercontinuum laser, which is also pulsed. For example, pulse synchronization can be performed so that the pulses emitted by the first and second laser units do not spatially overlap as they propagate in the nonlinear fiber, thus avoiding any adverse effects on the generation of the supercontinuum laser. However, for other applications (e.g., applications requiring constant light output), it is advantageous for the second laser unit to include a CW laser, which emits an additional laser in a continuous laser beam whose spectrum is outside that of the supercontinuum laser.

[0023] According to one embodiment, the second laser unit is configured to control the power of the additional laser independently of the supercontinuum laser. Independent control of the output power of each laser unit improves the flexibility of applying light to the sample.

[0024] Devices such as optical isolators can be installed to prevent light from the second laser unit from causing distortion in the seed laser.

[0025] According to another aspect, a microscope system is provided that includes the light generating device as described above. In particular, the microscope system may include a laser scanning microscope, wherein the laser emitted by the light generating device is used for fluorescence imaging. Attached Figure Description

[0026] The embodiments will now be described with reference to the accompanying drawings, in which... Figure 1 This is a schematic diagram of a microscope system including a light-generating device, used as a comparative example; Figure 2 This is a schematic diagram of a microscope system including a light generating device according to this embodiment; Figure 3 This is a schematic diagram of a microscope system including an alternative embodiment of a light-generating device; and Figure 4 This is a schematic diagram of a microscope system that includes an alternative embodiment of a light-generating device. Detailed Implementation

[0027] Figure 1 A microscope system 100 according to a comparative example is shown, which uses conventional methods to extend the spectrum of a supercontinuum laser.

[0028] Figure 1 The microscope system 100 includes a microscope 102 and a light generating device 104 optically coupled to the microscope 102. It should be noted that... Figure 1 Only those components of the microscope system 100 that contribute to understanding this disclosure are shown. In particular, the microscope system 100 may include... Figure 1 Additional components not shown. This also applies to... Figures 2 to 4 The example shown.

[0029] The light generation device 102 includes a white light laser source 106 configured to emit supercontinuum laser light. For example, the supercontinuum laser light emitted from the white light laser source 106 is assumed to be in the range of 440 nm to 800 nm. The supercontinuum laser light is transmitted through an optical fiber 108. One end 110 of the optical fiber 108 is connected to the white light laser source 106. The opposite end 112 of the optical fiber 108 faces a lens 114 through which the supercontinuum laser light enters free space, i.e., space not confined by optical fibers or the like.

[0030] The light generating device 104 includes an additional laser source 116 configured to emit monochromatic laser light of a specific wavelength that is outside the supercontinuum laser spectrum. In a comparative example, it is assumed that the wavelength of the laser light emitted by the additional laser source 116 is below the lower limit of the supercontinuum. For example, the additional wavelength may be assumed to be 405 nm.

[0031] Similar to supercontinuum light, the 405 nm laser beam is emitted into free space. To combine the supercontinuum laser with the monochromatic laser, a dedicated optical system is arranged in free space, comprising mirrors 118, 120, and 122, and a dichroic mirror 124. Mirrors 118, 120, and 122 reflect the supercontinuum and monochromatic laser beams onto the dichroic mirror 124, which is spectrally designed to combine the two laser beams through reflection and transmission, respectively. Using this free-space beam routing, the supercontinuum and monochromatic laser beams enter the microscope 102 along a common beam path.

[0032] Figure 1 The free-space beam routing shown has the following disadvantages: it requires optical elements (118 to 124) to guide the laser beam to the microscope 102. The optical elements (118 to 124) are not only expensive to set up, but also cumbersome to adjust.

[0033] Figure 2 A microscope system 200 according to an embodiment is shown, configured to avoid the above-mentioned... Figure 1 The problems illustrated by the comparative examples.

[0034] Microscope system 200 includes a microscope 202 (e.g., a laser scanning microscope) and a light generating device 204 optically coupled to the microscope 202. The light generating device 204 includes a first laser unit 206 and at least one second laser unit 208. The first laser unit 206 constitutes a white light laser source, while the second laser unit 208 comprises a monochromatic laser source. (As in...) Figure 1 In the comparative example, the white light laser source composed of the first laser unit 206 can be configured to generate supercontinuum lasers within a predetermined wavelength range (e.g., 440 nm to 800 nm), and the monochromatic laser source composed of the second laser unit 208 can be configured to generate monochromatic lasers with a specific wavelength (e.g., 405 nm).

[0035] The first laser unit 206 includes a seed laser 210 having a seed fiber 212 configured to transmit seed laser light emitted from the seed laser 210. The seed laser 210 may be a pulsed laser that outputs seed light into a laser cavity in the form of low-power NIR laser pulses. The laser cavity may include an optical fiber constituting the laser medium, preferably a Yb pump fiber (not shown).

[0036] The first laser unit 206 also includes a pump laser 214 having a pump fiber 216 configured to transmit pump laser light emitted from the pump laser 214. The pump laser 214 may be a CW laser that outputs pump light at high power.

[0037] exist Figure 2 In the illustrated embodiment, pump fiber 216 is connected to seed fiber 212. Pump laser 214 is configured to pump seed fiber 212 using high-power pump light from an amplified pulsed seed laser through pump fiber 216.

[0038] The first laser unit 206 also includes a nonlinear fiber 218 connected to the output end of the seed fiber 212. The nonlinear fiber 218 is configured to generate supercontinuum laser. For this purpose, the nonlinear fiber 218 can, for example, be composed of a photonic crystal fiber with a periodic microstructure capable of generating supercontinuum laser using nonlinear optical effects.

[0039] The first laser unit 206 includes a fiber arrangement 220, which comprises a nonlinear optical fiber 218. Figure 2 In the specific embodiment shown, fiber arrangement 220 further includes seed fiber 212 and pump fiber 216. Fibers 212, 216, and 218 of fiber arrangement 220 are interconnected (e.g., connected by spliced ​​fiber connections).

[0040] The second laser unit 208 includes a connecting optical fiber 222, which is coupled to one of the optical fibers 212, 216, and 218 of the fiber arrangement 220 of the first laser unit 206. Figure 2 In the illustrated embodiment, the connecting fiber 222 of the second laser unit 208 is directly spliced ​​to the nonlinear fiber 218. The optical connection to the nonlinear fiber 218 is used to spatially (and optically) combine the additional monochromatic laser generated by the second laser unit 208 with the supercontinuum laser generated by the first laser unit 206. Therefore, these two spectral components are transmitted together via the nonlinear fiber 218. Figure 2 In the embodiment shown, the nonlinear fiber 218 is coupled to the microscope 202, such that the combined laser is output directly from the nonlinear fiber 218 to the microscope 202.

[0041] The second laser unit 208 can be a solid-state laser, especially a diode laser in the form of a pigtail laser to which the optical fiber 222 is permanently fixed. This structure facilitates the arrangement of the second laser unit 208 within the light generating device 204.

[0042] The light generating device 204 may also include a single housing 224 configured to simultaneously house the first laser unit 206 and the second laser unit 208, thereby achieving a compact design. Figure 2In this configuration, the nonlinear optical fiber 218, which is wired outside the housing 224, forms the output of the light generating device 204.

[0043] The light generating device 204 may also include a controller (not shown) that can adjust the power of the additional monochromatic laser emitted by the second laser unit 208 independently of the power of the supercontinuum laser emitted by the first laser unit 206. In this way, the combined laser output of the light generating device 204 can be flexibly controlled relative to various spectral laser components.

[0044] Figure 3 and Figure 4 Alternative embodiments of the light generating apparatus 204 are shown. In the following description, only those of these improved embodiments will be used in conjunction with... Figure 2 The different features shown are... Figure 2 The corresponding components shown are indicated by the same reference numerals.

[0045] exist Figure 3 In the illustrated embodiment, the light generating device 204 includes an output optical fiber 326, which is wired outside the housing 224 and connected to the microscope 202. Inside the housing 224, the output optical fiber 326 is connected to the output end of the nonlinear optical fiber 218. Furthermore, a connecting optical fiber 222 of the second laser unit 208 is connected to the output optical fiber 326 to combine the additional monochromatic laser generated by the second laser unit 208 with the supercontinuum laser generated by the first laser unit 206. Similarly, the aforementioned fiber connections can also be achieved by splicing.

[0046] Therefore, according to Figure 3 In the embodiment described above, the output of the light generating device 204 is formed by the output optical fiber 326, rather than as shown in the example. Figure 2 The nonlinear fiber 218 is shown in the configuration. For the different spectral components emitted by the first laser unit 206 and the second laser unit 208, the output fiber 326 forms a common transmission fiber, and these spectral components are subsequently combined within the housing 224. For this purpose, the connecting fiber 222 of the second laser unit 208 is directly connected to the output fiber 326 instead of the nonlinear fiber 218.

[0047] Figure 4 An alternative is shown in which the connecting fiber 222 of the second laser unit 208 (e.g., by splicing) is directly connected to the seed fiber 212 of the first laser unit 206, instead of... Figure 2 Connect to the nonlinear fiber 218 as shown in the configuration.

[0048] The aforementioned improved scheme for the fiber optic connection between the first laser unit 206 and the second laser unit 208 can be flexibly implemented because the monochromatic laser generated by the second laser unit 208 is only spatially combined with the laser generated by the first laser unit 206, without affecting the supercontinuum generation process. In other words, the additional laser can be coupled to the fiber arrangement 220 at any point within the housing 224.

[0049] The above embodiments should be understood as non-limiting examples only. Therefore, according to Figures 2 to 4 In the illustrated embodiment, the additional laser generated by the second laser unit 208 is monochromatic. However, the second laser unit 208 can also be configured to add a continuous wavelength range to the supercontinuum spectrum provided by the first laser unit 206. Furthermore, according to the above embodiment, only one additional laser unit is provided to extend the wavelength spectrum. However, depending on the specific application, the laser generating apparatus may include more than one laser unit in addition to the first laser unit that provides the supercontinuum spectrum.

[0050] Elements that are identical or have similar functions are represented by the same reference numerals in all figures. The term "and / or" as used herein includes one or more related listed items and all combinations thereof, and may be abbreviated as " / ".

[0051] Although some aspects are described in the context of an apparatus, they also clearly represent a description of the corresponding method, in which a block or device corresponds to a method step or a feature of a method step. Similarly, aspects described in the context of a method step also represent a description of a corresponding block or item or feature of the corresponding apparatus.

[0052] Figure Labels 100 Microscope Systems 102 Microscope 104 Light Generating Device 106 White Light Laser Source 108 fiber optic cables 110 and 112 fiber ends 112 Lighting equipment 114 Lenses 116 Additional laser source 118, 120, 122 reflectors 124 Dichroic Mirror 200 Microscope System 202 Microscope 204 Light Generating Device 206 First Laser Unit 208 Second Laser Unit 210 Seed Laser 212 seed optical fiber 214 Pumped Laser 216 Pumped Fiber 218 Nonlinear optical fiber 220 fiber arrangement 222 Connecting fiber optic cables 224 Housing 326 Output fiber.

Claims

1. A light generating device (204) for a microscope (202), comprising: A first laser unit (206) comprises a fiber arrangement (220) consisting of optical fibers (212, 216, 218), the fiber arrangement including a nonlinear optical fiber (218) configured to generate a supercontinuum laser; and At least one second laser unit (208) is configured to generate an additional laser whose spectrum is outside that of the supercontinuum laser. The second laser unit (208) includes a connecting optical fiber (222) connected to one of the optical fibers (212, 216, 218) of the fiber arrangement (220) of the first laser unit (206) to spatially combine the additional laser and the supercontinuum laser.

2. The light generating device (204) according to claim 1, wherein, The additional laser is independent of the generation of the supercontinuum laser.

3. The light generating apparatus (204) according to claim 1 or 2, wherein, The first laser unit (206) includes a seed laser (210) and a pump laser (214), the seed laser (210) having a seed fiber (212) configured to transmit the seed laser, and the pump laser (214) having a pump fiber (216) configured to transmit the pump laser. The fiber arrangement (220) of the first laser unit (206) includes the seed fiber (212), the pump fiber (216) and the nonlinear fiber (218). The nonlinear optical fiber (218) is directly or indirectly coupled to the seed optical fiber (212) and the pump optical fiber (216) to generate the supercontinuum laser based on the seed laser and the pump laser.

4. The light generating device (204) according to claim 3, wherein, The connecting fiber (222) of the second laser unit (208) is connected to one of the seed fiber (212), the pump fiber (216), or the nonlinear fiber (218).

5. The light generating device (204) according to claim 4, wherein, The fiber arrangement (220) of the first laser unit (206) includes an output fiber (326) connected to the output end of the nonlinear fiber (218). The connecting optical fiber (222) of the second laser unit (208) is connected to the output optical fiber (326).

6. The light generating apparatus (204) according to any one of the preceding claims, wherein, The connecting optical fiber (222) of the second laser unit (208) is coupled to the fiber arrangement (220) of the first laser unit (206) via spliced ​​optical fiber connection.

7. The light generating apparatus (204) according to any one of the preceding claims, wherein, The second laser unit (208) is composed of a single laser module, and the connecting optical fiber is firmly attached to the single laser module.

8. The light generating device (204) according to any one of the preceding claims, comprising a single housing (224), wherein the first laser unit (206) and the second laser unit (208) are jointly housed in the housing.

9. The light generating apparatus (204) according to any one of the preceding claims, wherein, The second laser unit (208) is configured to generate the additional laser having a single wavelength.

10. The light generating apparatus (204) according to any one of the preceding claims, wherein, The second laser unit (208) is configured to generate the additional laser with a wavelength smaller than the minimum wavelength of the supercontinuum laser.

11. The light generating apparatus (204) according to any one of the preceding claims, wherein, The second laser unit (208) includes a diode laser.

12. The light generating apparatus (204) according to any one of the preceding claims, wherein, The second laser unit (208) includes a pulsed laser.

13. The light generating apparatus (204) according to any one of the preceding claims, wherein, The second laser unit (208) is configured to control the power of the additional laser independently of the power of the supercontinuum laser.

14. The light generating apparatus (204) according to any one of the preceding claims, wherein, The nonlinear optical fiber (218) is a photonic crystal fiber.

15. A microscope system (200) comprising a light generating device (204) according to any one of the preceding claims.

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