Optical waveguide

Abstract

To provide an optical waveguide device in the field of mid-infrared photonics and a method for manufacturing such a device.SOLUTION: The device comprises a fluoride glass substrate having a local concentration of a chemical element at an internal contact and a waveguide inscribed along a path defined in the substrate. The waveguide is formed by directing a focused ultra-short laser pulse into the substrate and scanning the pulse to induce migration and densification of chemical elements at the inner contacts, resulting in a positive refractive index contrast. Fluoride glass substrates can include zirconium fluoride and modifiers such as barium fluoride, aluminum fluoride, and rare earth elements to enable optical gain. The described technology further encompasses an integrated photonics device including a waveguide laser with mirrors and gratings defining a laser cavity for use in sensing, communications, and laser systems.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to optical waveguide devices, methods of forming waveguides, and optical devices. [Background technology]

[0002] Any reference to prior art methods, devices, or documents should not be construed as constituting any evidence or admission that they form part of the common general knowledge.

[0003] In recent years, the field of integrated photonics has made significant progress, particularly in the development of optical waveguides for applications such as sensing, communications, and laser systems. Despite these advances, it remains challenging to create efficient and reliable visible to mid-infrared (MIR) optical waveguides due to material properties and fabrication techniques.

[0004] Traditional materials such as silica glass, phosphate glass, and germanate glass have been extensively investigated for waveguide applications due to their favorable optical properties. However, these materials have a low optical transmission rate of approximately 1100 cm for silicates. -1 , 1250 cm for phosphate -1 , and 900 cm for germanate. -1 These high phonon energies result in significant losses when these materials are used in mid-infrared applications, thereby limiting their effectiveness in this wavelength range.

[0005] Fluoride glasses, especially those based on zirconium fluoride (ZrF4), are characterized by their low phonon energy (400-600 cm -1 Fluoride glasses have shown considerable promise due to their broad transparency, low refractive index, and favorable thermal and mechanical properties. These properties make them particularly suitable for mid-infrared applications. However, creating high-quality waveguides in fluoride glasses has proven difficult.

[0006] Initial efforts to create waveguides in fluoride glasses involved ion-exchange techniques, such as exchanging fluoride ions with chloride or alkali metal ions (e.g., lithium, sodium, potassium). While some success was achieved, these methods often resulted in severe devitrification, slow exchange rates, and poor control over the waveguide structure. Furthermore, using mask materials to define the waveguide channels proved extremely difficult due to compatibility issues and the tendency of the masks to corrode the glass surface.

[0007] Another approach that was tried was to deposit fluoride glass on the substrate using physical vapor deposition. While this method offered some control over waveguide formation, it proved too complicated and did not produce the desired high positive refractive index change necessary for efficient MIR waveguiding.

[0008] The introduction of ultrashort (<10 ps) pulsed laser micromachining offered a novel technique for fabricating waveguides in fluoride glasses. Early studies demonstrated the feasibility of using ultrashort laser pulses to induce refractive index changes. However, achieving a significantly positive refractive index change suitable for type-1 waveguides became questionable. Early reports included low refractive index changes (up to 3 × 10 -3 ), which was insufficient for practical MIR applications. Attempts to scale up this process often resulted in the formation of negative refractive index change zones, which prevented efficient confinement of light within the waveguide.

[0009] Technical challenges in the field of mid-infrared photonics necessitate the development of reliable and efficient methods for fabricating highly positive refractive index-change type-1 waveguides in fluoride glasses. Existing techniques, including ion exchange, physical vapor deposition, and ultrashort-pulse laser micromachining, have failed to achieve the desired levels of refractive index change, control over waveguide structure, and low propagation losses required for practical applications. The lack of such suitable fabrication methods has hindered the integration of shortwave to mid-infrared optical waveguides into advanced photonics systems and devices, limiting their potential applications in areas such as sensing, communications, and laser technology. Summary of the Invention [Means for solving the problem]

[0010] In one aspect, the present invention provides a fluoride glass substrate configured with an internal contact having a concentration of a chemical element of the fluoride glass substrate; and a waveguide inscribed in the fluoride glass substrate along a path defined by the internal contact, the waveguide comprising: an 8×10 -3 and a waveguide having a positive refractive index contrast of greater than .

[0011] In another aspect, the present invention provides a waveguide formed in a fluoride glass substrate, the fluoride glass substrate configured to have a concentration of a chemical element of the fluoride glass substrate at an internal contact to form a waveguide therein, the waveguide having a concentration of at least 8×10 -3 has a positive refractive index contrast exceeding

[0012] In another aspect, the invention provides a method for forming a fluoride glass substrate using a laser beam, the method comprising the steps of directing a focused laser pulse into the substrate, scanning the laser pulse across the substrate to etch a waveguide therein, thereby inducing a concentration of a chemical element in the fluoride glass substrate at or around the inner contact point, and forming a fluoride glass substrate using a laser beam. -3 and forming a waveguide having a positive refractive index contrast greater than or equal to 1.0.

[0013] In one aspect, the invention provides a fluoride glass substrate configured or modified with internal contacts such that there is a local increase in the concentration of a chemical element of the fluoride glass, and a waveguide inscribed along a path defined by translating the internal contacts in three dimensions in any desired pattern within the substrate, the waveguide being etched along a path defined by translating the internal contacts in three dimensions in any desired pattern, the waveguide being etched along a path defined by translating the internal contacts in three dimensions in any desired pattern within the substrate ... -3 and a waveguide having a positive refractive index contrast of greater than .

[0014] In another aspect, the present invention provides a waveguide formed in a fluoride glass substrate, the fluoride glass substrate being configured or modified at an internal contact to have a local increase in concentration of a chemical element of the fluoride glass substrate to form a waveguide therein, the waveguide having a density of 8×10 -3 has a positive refractive index contrast exceeding

[0015] In another aspect, the invention provides a method for forming a waveguide in a fluoride glass substrate by directing a focused laser pulse into the substrate and scanning the laser pulse across the substrate at a scan rate to inscribe a waveguide therein, thereby inducing a local increase in the concentration of a chemical element in the fluoride glass substrate at the internal contact point, and forming a waveguide therein by injecting a fluoride glass substrate with a local increase in the concentration of a chemical element at the internal contact point. -3 and forming a waveguide having a positive refractive index contrast greater than or equal to 1.0.

[0016] In another aspect, the present invention provides a glass substrate configured with a concentration of a chemical element of the glass substrate at an internal contact, and a waveguide inscribed in the glass substrate along a path defined by the internal contact, the waveguide comprising: an 8×10 -3 and a waveguide having a positive refractive index contrast of greater than .

[0017] Preferably, the fluoride glass substrate comprises ZrF4 and a modifier selected from the group consisting of BaF2, AlF3, NaF, ErF3, YbF3, and CeF3.

[0018] Preferably, the waveguide is 1 μm 2 ~2500μm 2 and optionally a length in the range of 1 mm to 50 mm.

[0019] Preferably, the fluoride glass substrate is configured to have a concentration of one or more chemical elements at the inner contacts.

[0020] Preferably, the one or more chemical elements concentrated in the fluoride glass substrate are selected from the alkaline earth group (II) and / or the lanthanide series. Preferably, the one or more chemical elements concentrated in the fluoride glass substrate include one or more of barium (Ba), cerium (Ce), ytterbium (Yb), strontium (Sr), calcium (Ca), and erbium (Er).

[0021] Preferably, the one or more chemical elements concentrated in the fluoride glass substrate include one or more of lanthanum and cerium.

[0022] Preferably, the positive refractive index contrast is achieved through densification of the fluoride glass substrate by increasing the concentration of elements at or around the inner contacts.

[0023] Preferably, the fluoride glass substrate further contains a rare earth element to improve laser processing characteristics.

[0024] Preferably, the waveguide is inscribed using an ultrashort pulse laser with a pulse duration in the range of 10 to 500 femtoseconds.

[0025] Preferably, the glass substrate comprises a composition having amorphous properties, and more preferably, the fluoride glass substrate comprises a composition having amorphous properties.

[0026] Preferably, the glass substrate is a halogen glass substrate.

[0027] Preferably, the glass or fluoride glass substrate consists mainly of halogen anions with an oxide anion content of less than 5 mole %.

[0028] Preferably, lanthanum (Ln) is absent and / or excluded from the composition of the glass substrate.

[0029] Preferably, the laser pulses have a repetition rate in the range of 1 kHz to 200 kHz.

[0030] Preferably, the laser is scanned across the fluoride glass substrate at a scanning speed ranging from 5 micrometers per second (μm / s) to 500 micrometers per second (μm / s), and more preferably from 40 to 150 μm / s.

[0031] Preferably, the energy per pulse of the laser is in the range of 100 nJ to 10000 nJ.

[0032] Preferably, the laser pulses have a wavelength in the range of 190 nm to 1600 nm.

[0033] Preferably, the waveguide is formed by a single translation of the laser focus.

[0034] Preferably, the waveguide is formed by multiple translations of the inner contacts, each separated perpendicular to the direction of translation by between 200 nm and 3500 nm.

[0035] Preferably, the waveguide is formed by continuous movement of a laser focal point along a predefined path within the fluoride glass substrate. Alternatively, the waveguide is formed by movement of the fluoride glass substrate along a predefined path through a laser focal point.

[0036] Preferably, the energy per pulse is in the range of 2 to 6 μJ.

[0037] Preferably, multiple scans are performed with a multi-scan pitch of 1 μm.

[0038] Preferably, the laser cavity is formed using broadband butt-coupled high reflectivity (HR) mirrors and fiber Bragg gratings to lase the active waveguide at a wavelength of about 1542.83 nm.

[0039] Preferably, the laser is configured with an energy per pulse in the range of 2-6 μJ, a feed rate in the range of 40-150 μm / s, and a multi-scan pitch of 1 μm.

[0040] Preferably, the fluoride glass substrate includes elements selected to provide optical gain at one or more wavelengths in the range of 190 nm to 7000 nm.

[0041] In one aspect, the present invention provides a method for producing a pharmaceutical composition comprising: a fluoride glass substrate configured to have a concentration of a chemical element of the fluoride glass substrate at an interior contact that defines a waveguide path; and a waveguide inscribed in the substrate along the waveguide path, the waveguide having an 8×10 -3 an optical waveguide device comprising a waveguide having a positive refractive index contrast greater than a mirror disposed at one end of a waveguide formed in a substrate of the optical waveguide device; a grating disposed at the end of the waveguide opposite the mirror.

[0042] Preferably the mirror is a high reflectivity (HR) mirror designed to reflect a wide range of wavelengths. Preferably the mirror is a broadband butt-coupled high reflectivity (HR) mirror.

[0043] Preferably, the grating comprises an optical grating.

[0044] Preferably, the grating is a fiber Bragg grating (FBG) that is designed to reflect a particular wavelength or range of wavelengths.

[0045] Preferably, the optical device further comprises a laser source configured to provide energy to the optical waveguide device to enable laser processing.

[0046] Preferably, the mirrors and grating form a laser cavity operating at a wavelength of 1542.83 nm.

[0047] Preferably, the waveguides are formed by directing focused ultrashort laser pulses into the substrate and scanning the laser pulses across the substrate to inscribe the waveguide structure.

[0048] In another aspect, the present invention provides a fluoride glass substrate and a waveguide etched into the substrate, the waveguide comprising: an 8×10 -3 and a waveguide having a positive refractive index contrast of greater than .

[0049] Preferred features, embodiments, and variations of the present invention can be identified from the following detailed description, which provides sufficient information for those skilled in the art to practice the invention. The detailed description should not be considered in any way to limit the scope of the above summary of the invention. The detailed description will make reference to several drawings, such as: [Brief explanation of the drawings]

[0050] [Figure 1] 1 illustrates an optical waveguide device according to various embodiments. [Figure 2] 1 illustrates a glass substrate prior to being adapted to concentrate elements therein. [Figure 3] 1 illustrates a glass substrate showing the internal contacts and the waveguide paths defined by the laser pulses. [Figure 4] 1 illustrates a glass substrate after being subjected to a laser pulse that causes elemental concentration at or around the inner contact. [Figure 5] 1 illustrates an optical waveguide device having a waveguide formed therein with an element concentrated around the waveguide. [Figure 6]1 illustrates a method for forming a waveguide in a glass substrate. [Figure 7] 1 illustrates an optical device incorporating an optical waveguide device according to various embodiments. [Figure 8] 10 is a differential interference contrast microscope image illustrating three waveguides, each 12 μm wide, written with parameters of 50 kHz and 4 μJ (the feed rate and observation pitch of the waveguides are provided on each image). [Figure 9] Illustrated is the refractive index map for a waveguide inscribed with 4 μJ energy, a 40 μm / s feed rate, and a 1 μm pitch. [Figure 10] Figure 1 shows the BSE, DIC, and elemental maps of a waveguide inscribed with 4 μJ energy, 40 μm / s feed rate, and 1 μm pitch. Ba, Ce, Yb, and Er appear to enhance the positive index change zone, while Na, Al, and Zr appear to enhance the negative index change zone. [Figure 11] (a) and (b) illustrate the 3.5 μm laser mode propagated through the waveguide shown in FIG. 9, and (c) and (d) illustrate the simulated mode corresponding to the same refractive index map (the Poynting vector (SZ) profile in the propagation direction is shown). [Figure 12] 1 is a schematic diagram of a compact laser cavity. [Figure 13] FIG. 1 illustrates the physical setup of a compact laser cavity. [Figure 14] FIG. 1 illustrates the laser output power obtained with pumping a 120 mW 980 nm laser. [Figure 15] FIG. 1 illustrates the laser output power obtained with pumping a 120 mW 980 nm laser. DETAILED DESCRIPTION OF THE INVENTION

[0051] Embodiments of the present invention relate to optical waveguides in glass substrates. Optical waveguides are structures that guide light waves with minimal signal loss, making them fundamental building blocks in photonics. Embodiments of the present invention use ultrashort pulsed laser techniques to inscribe waveguides in glass substrates, resulting in waveguides that exhibit high positive refractive index contrast and thereby improved optical properties.

[0052] 1 illustrates an optical waveguide device 101 according to various embodiments. The optical waveguide device 101 includes a glass substrate in the form of a fluoride glass substrate 103 and a waveguide 105 inscribed therein. The waveguide 105 is preferably an optical waveguide, and multiple optical waveguides can be formed within the fluoride glass substrate 103.

[0053] The fluoride glass substrate 103 comprises ZrF4 and a modifier selected from the group consisting of BaF2, AlF3, NaF, ErF3, YbF3, and CeF3.

[0054] In one embodiment, the fluoride glass substrate 103 includes ZrF4, BaF2, AlF3, NaF, ErF3, YbF3, and CeF3. More specifically, the composition of the fluoride glass substrate 103 may be 51.3ZrF4, 19BaF2, 3AlF3, 19.45NaF, 0.5ErF3, 1.75YbF3, 5CeF3 [mol %].

[0055] In some embodiments, lanthanum (Ln) may be absent and / or excluded from the composition of the glass substrate due to potentially unwanted effects.

[0056] While the above embodiments include fluoride glass substrates, it will be understood that other halogen-containing glass substrates (e.g., chloride or bromide glasses) may be suitable. Thus, while a fluoride glass substrate may consist primarily of halogen anions with an oxide content of less than 5 mole percent, the present principles can be applied to any glass substrate consisting primarily of halogen ions with an oxide content of less than 5 mole percent. In one example, a fluoride glass substrate may consist primarily of any cation bonded to fluorine anions; if any other anions are present, the concentration of those other anions should be less than 5 mole percent.

[0057] 1-5, the fluoride glass substrate 103 is configured to have an enrichment of chemical element E in the fluoride glass substrate 105 at inscription points X that define paths sometimes referred to as waveguide paths 107. This enrichment of chemical element E may also be defined as a local increase in the concentration of chemical element E at the inscription points. It should be noted that the concentration of element E generally remains constant in untreated fluoride glass substrates. These inscription points X define paths within the substrate along which the waveguides 105 are inscribed. By enriching chemical element E at these inscription points X, the waveguides 105 can be inscribed with a concentration of 8×10 -3 In some embodiments, the waveguide 105 exhibits a positive refractive index contrast of greater than 2×10 -2 The refractive index contrast may be greater than .

[0058] The fluoride glass substrate 103 may be configured to have a concentration of elements at or around the internal junction X to further improve the optical properties of the waveguide 105.

[0059] The enrichment of element E (which may be considered the first element for some applications and embodiments) in a glass substrate should be understood as the relative enrichment of that element E in the glass substrate at or around the internal contact point X. Therefore, enrichment of element E in a glass substrate includes laser-induced movement or migration of an element from a first point or region of the glass substrate (e.g., as shown in FIG. 2) to a second point in the form of internal contact point X (as shown in FIGS. 3 to 5) according to the method described below. For completeness, the above will be understood to refer to the migration of adjacent element E to the internal contact point. Therefore, element E can still be present in areas of the fluoride glass far from the internal contact point. Furthermore, there may be a gradient near the internal contact point. Alternatively or additionally, enriching a chemical element can be understood as increasing the density of that chemical element at and / or around the internal contact point.

[0060] In some embodiments, the concentration of element E at or around internal junction X may involve the migration or exchange (not shown) of a second element away from internal junction X, such that the second element moves from the second point (internal junction X) to the first point previously occupied by element E (the first element).

[0061] The element E enriched in the glass substrate, and in particular in the intact fluoride glass substrate 103 in some embodiments, can be selected from the group including, and in some embodiments consisting of, barium (Ba), cerium (Ce), ytterbium (Yb), erbium (Er), strontium (Sr), and calcium (Ca).

[0062] In some embodiments, the chemical elements concentrated in the fluoride glass substrate include one or more of lanthanum and rare earth elements. For example, the chemical elements concentrated in the fluoride glass substrate may include lanthanum and one or more of cerium, ytterbium, and erbium. In another example, the chemical elements concentrated in the fluoride glass substrate may include one or more of cerium, ytterbium, and erbium.

[0063] In some embodiments, the waveguide 105 can have a length in the range of 1 mm to 50 mm. In some embodiments, the waveguide 105 can have a length of at least 10 mm. In some other embodiments, the waveguide 105 can have a length of at least 12 mm.

[0064] The waveguide 105 formed in the glass substrate may have a cross-sectional diameter or width between 2 micrometers and 50 micrometers. In some embodiments, the waveguide 105 may have a cross-sectional diameter or width between 12 micrometers and 14 micrometers. In some embodiments, the waveguide 105 may have a cross-sectional width of about 12 micrometers. In some embodiments, the waveguide 105 may have a cross-sectional height of 14 micrometers. In one embodiment, the waveguide 105 is about 12 micrometers wide and about 14 micrometers high.

[0065] In some embodiments, the waveguide is 1 μm 2 ~2500μm 2 The cross-sectional diameters and / or areas achieved by the waveguide embodiments disclosed herein are smaller than waveguides, such as, for example, depressed clad waveguides, that are achievable through several known techniques. This makes the disclosed waveguide embodiments particularly well suited for photonics applications, including photonic integrated circuits (PICs).

[0066] As mentioned above, the optical waveguide device 101 can be fabricated by forming the optical waveguides 105 in a glass substrate through direct laser writing, a method for doing so is described below.

[0067] FIG. 6 shows a method for forming an optical waveguide in a glass substrate.

[0068] In the first step, a glass substrate is prepared in step 600 .

[0069] In the second step, a laser pulse is directed into the glass substrate in step 605. The laser pulse may be a focused ultrashort laser pulse.

[0070] In the third step, in step 610, a laser pulse is scanned across the glass substrate to inscribe a waveguide therein.

[0071] The laser pulse creates a local change in the glass substrate, enhancing the refractive index at the internal contact point. The waveguide can therefore be understood to be formed by the continuous movement of the laser focus along a predefined path (or waveguide path) within the glass substrate.

[0072] The scanning operation may be performed at a predetermined scan speed and may include one or more scans. In some embodiments, multiple scans are performed in step 615. In some embodiments, the multiple scans are performed at a pitch between about 1 micrometer and about 2.5 micrometers. In some embodiments, the pitch between scans is anywhere between about 1 micrometer and about 2 micrometers. In some embodiments, the pitch is 1 micrometer, or 1.5 micrometers, or 2 micrometers.

[0073] The scanning operation may also include one or more translations at optional step 620. In some embodiments, the waveguide is formed by a single translation of the laser pulse. In some embodiments, the waveguide is formed by multiple translations of the inner contact points, each spaced 200 nm to 3500 nm apart perpendicular to the translation direction.

[0074] The combination of laser pulses directed at the glass substrate during the scanning operation induces a concentration of the chemical element in the glass substrate at or around the inner contact, thereby increasing the density of the chemical element at or around the inner contact, and the density of the chemical element increases by 2×10 -2 In some embodiments, greater than 8×10 -3 A waveguide having a positive refractive index contrast greater than .gtoreq..times ...

[0075] In one embodiment, a fluoride glass substrate as described throughout is provided in step 600 .

[0076] In step 605, a focused ultrashort laser pulse is directed into the fluoride glass substrate.

[0077] In some embodiments, the laser pulses have a repetition rate in the range of 1 kHz to 200 kHz, and in some embodiments, a repetition rate of about 50 kHz.

[0078] In some embodiments, the energy per pulse ranges from 100 nanojoules to 10,000 nanojoules. In some embodiments, the energy per pulse ranges from 2,000 nanojoules to 6,000 nanojoules, and may range from 2,000 nanojoules to 5,000 nanojoules. In some embodiments, the energy per pulse may be about 2 microjoules or 2,000 nanojoules. In some embodiments, the energy per pulse may be about 4,000 nanojoules.

[0079] In some embodiments, the laser pulses have a wavelength in the range of 190 nm to 1600 nm, hi some embodiments, the laser pulses have a wavelength of 1030 nm.

[0080] In step 610, a laser pulse is scanned across the glass substrate at a scanning speed to inscribe a waveguide into the glass substrate at or around the internal contact point defined by the scanning motion of the laser. The scanning speed may range from 5 micrometers per second to 500 micrometers per second. In some embodiments, the scanning speed may range from 40 micrometers per second to 150 micrometers per second. In some embodiments, the scanning speed may be about 80 micrometers per second. In other embodiments, the scanning speed may be about 40 micrometers per second. In some embodiments, the scanning speed may be one of 40 micrometers per second, 80 micrometers per second, 120 micrometers per second, and 150 micrometers per second.

[0081] The laser pulses may have a pulse duration in the range of 10 femtoseconds to 500 femtoseconds, hi some embodiments, the laser pulses may have a pulse duration of 240 femtoseconds.

[0082] The laser pulses can be focused using a focusing device, for example, a microscope objective, or one or more lenses, or curved mirrors, to focus the laser spot to a diameter of 250 nm to 50 μm.

[0083] As mentioned above, this induces a concentration of a chemical element (e.g., barium) in the fluoride glass substrate at or around the inner contact defined by the scanning motion of the laser, resulting in a concentration of 2×10 -2 and in some embodiments, greater than 8×10 -3 3. Forming a waveguide having a positive refractive index contrast therein that exceeds

[0084] In some embodiments, the chemical elements concentrated in the fluoride glass substrate include one or more rare earth elements.

[0085] In some embodiments, the chemical elements enriched in the fluoride glass substrate are selected from the alkaline earth group (II) and / or the lanthanide series.

[0086] In some embodiments, the fluoride glass substrate includes (or is doped with) elements selected to provide optical gain at one or more wavelengths in the range of 190 nm to 7000 nm. These elements selected to provide optical gain can include rare earth elements.

[0087] Exemplary Embodiments of Optical Waveguide Devices In one embodiment, the fabrication conditions for forming the waveguide 105 in the glass substrate 103 include an energy per pulse in the range of 2-6 μJ, a feed rate in the range of 40-150 μm / s, and a multi-scan pitch of 1 μm. The resulting waveguide is approximately 12 μm wide and 14 μm high, which in turn results in multimode behavior at a wavelength of 3.5 μm, and the waveguide has a propagation loss as low as 0.21 dB / cm measured at a wavelength of 1.62 μm.

[0088] The optical waveguide device 101 can be incorporated into an optical device 700, which can be seen in FIG.

[0089] The optical device 700 includes an optical waveguide device 101 according to various embodiments described herein, a mirror 701 disposed at one end of a waveguide formed in a glass substrate of the optical waveguide device 101, and a grating 703 disposed at the end of the waveguide opposite the mirror 701.

[0090] The placement of mirrors 701 and gratings 703 at opposite ends of the waveguide creates a cavity that can be used to lase the waveguide at a desired wavelength, thus forming a waveguide laser.

[0091] Mirror 701 can take the form of a highly reflective mirror that reflects a wide range of wavelengths, hi one embodiment, mirror 701 takes the form of a broadband butt-coupled highly reflective mirror.

[0092] Grating 703 may take the form of an optical grating, although other gratings may be used, such as, for example, a diffraction grating or a distributed feedback grating.

[0093] In some embodiments, an optical grating in the form of a distributed feedback (DFB) grating may be written directly into the waveguide to realize a distributed feedback laser.

[0094] In some embodiments, an optical grating in the form of a fiber Bragg grating (FBG) is provided to reflect a particular wavelength or range of wavelengths required.

[0095] The optical device 700 can include a laser source 705 for providing energy to the waveguide.

[0096] Exemplary Embodiments of Optical Devices In one embodiment, the optical device includes a laser source connected to a fiber Bragg grating (FBG) disposed at the end of a waveguide formed in a fluoride glass substrate as described throughout. A broadband butt-coupled high reflectivity is disposed at the opposite end of the waveguide, thereby forming a cavity in combination with the FBG.

[0097] The laser source is configured to provide 120 mW of light or energy at a wavelength of 976 nm through a medium (eg, fiber) that is coupled to the FBG.

[0098] This embodiment has been observed to have an emission peak centered at about 1542.83 nm.

[0099] Experimental results A commonly used composition for ultrashort pulse laser inscription is 53ZrF4, 20BaF2, 3LaF3, 4AlF3, 20NaF (mol%). Apart from refractive index change, tuning of the optical, mechanical, and thermal properties can be achieved by varying the modifiers in the composition.

[0100] The following discussion focuses on modifying the network modifying components rather than the previous ones in the general ZBLAN formulation.

[0101] To further increase the magnitude of the positive refractive index achieved by laser inscription, LaF was removed, leaving the glass with one polyvalent glass modifier, since AlF is essentially a conditional glass former. The final composition was 51.3ZrF, 19BaF, 3AlF, 19.45NaF, 0.5ErF, 1.75YbF, and 5CeF (mol%).

[0102] The rare earth elements were doped and used in the waveguide to fabricate the chip laser. 3+ is doped 4I 11 / 2 State Er 3+ and 4F 7 / 2 State Ce 3+ The 1.5 μm erbium emission is increased by resonant energy transfer between the former and the latter. 3 / 2 →4I1 5 / 2 Enhanced 1.5 μm emission. The glasses were prepared using conventional melt quenching techniques at the Le Verre Fluore industrial facility in Brittany, France.

[0103] The final waveguide was inscribed using a Pharos femtosecond laser system operating at a central wavelength of 1030 nm and a pulse duration of 240 fs and a repetition rate of 50 kHz.

[0104] Lower repetition rates provide ideal engraved windows for multi-scan waveguides in fluoride glass. Therefore, parametric studies for this recomposed glass were conducted over the range of 1 to 250 kHz. 50 kHz was found to be ideal for creating large positive index change waveguides. Introducing the correct amount of spherical aberration by detuning the focusing objective (Olympus LUCPlan FL N, 0.6 NA, 40X) helped optimize the achievable index change of the waveguide depending on the collar position.

[0105] A 500 μm collar position was found to be optimal. All waveguides were inscribed to a depth of 170 μm.

[0106] The waveguides in the glass samples were multiscan type 1. A differential interference contrast (DIC) microscope image is shown in Figure 8. A single laser scan pass created a modified strand of waveguide approximately 1 μm wide and 12–14 μm high. The 12 μm-wide waveguides were fabricated by laterally shifting each scan by a preset pitch of 1, 1.5, 2, or 2.5 μm. The total number of scans was adjusted to maintain a 12 μm waveguide width. The optimal fabrication window in terms of morphology was inscribed with energies per pulse ranging between 2–6 μJ, feed rates ranging between 40–150 μm / s, and a multiscan pitch of 1 μm. Outside this window, either the refractive index contrast was weak or a strong discontinuity in the refractive index contrast occurred. Figure 8 shows that the waveguide has a negative refractive index change at the top (black) and a positive refractive index change at the bottom (white), characteristic of multiscan waveguides.

[0107] The refractive index change of the waveguide was measured using a Rinck near-field refractometer, as shown in Figure 9. The waveguide was fabricated with an energy of 2 μJ and a feed rate of 80 μm / s. The positive refractive index change of this waveguide was 2 × 10 -2 The large drop in refractive index at the top of the waveguide increases the effective index seen by the propagating mode.

[0108] The positive refractive index change is linked to a densification of the material, clearly discernible in backscattered electron (BSE) microscopy images using Z-contrast (Figure 10), where Z corresponds to the atomic number. The negative refractive index region exhibits the presence of nanovoids, a phenomenon previously documented in multiscan waveguide studies in both ZBLAN and fused silica. In particular, distinct horizontal rows of nanovoids were observed, separated from the main negative refractive index region. Furthermore, the stripe of material located at the base of the waveguide, as indicated by the red bracket in the differential interference contrast (DIC) image, is absent in both the backscattered electron (BSE) image and elemental mapping. This absence could be due to thermally induced diffusion or polarizability changes, which clearly indicate a simple refractive index change that would not result in differences in the BSE image or elemental mapping. This behavior has been extensively described in the context of fused silica.

[0109] Through comprehensive elemental mapping of the waveguide and its surroundings, the inventors discovered that the positive refractive index contrast is primarily the result of densification caused by the migration of certain elements within the fluoride glass substrate. These elements have been identified as barium (Ba), calcium (Ca), strontium (Sr), cerium (Ce), ytterbium (Yb), and erbium (Er). By increasing the concentration of Ba in the fluoride glass substrate and observing the potential of the Ce signal overlapping with Ba and thereby mimicking its behavior, the inventors conclude that Ba is the primary contributor to the positive refractive index contrast. The inventors have discovered that certain alkaline earth group (Group II) and lanthanide series elements are observed to migrate away from zones exhibiting negative refractive index contrast and into regions exhibiting positive refractive index contrast. Conversely, the inventors have discovered migration of Na (sodium), Zr (zirconium), and Al (aluminum) from the positive refractive index contrast region to the negative refractive index contrast region. That is, these elements were found to accumulate in the regions exhibiting a negative refractive index change. Fluorine was observed to accumulate in the negative refractive index contrast zone without any evacuation or migration from elsewhere. The inventors believe that this Z contrast arises from microvoids filled with fluorine gas, similar to observations reported in fused silica.

[0110] Laser modes with a diameter of 3.5 μm were propagated through the waveguide, and due to its high refractive index change, they became multimode. Experimentally, two modes, namely, the fundamental mode and higher-order modes, could be observed. A lateral shift of the fiber that launches the laser modes into the waveguide helps to excite higher-order modes and / or the fundamental mode (Figures 11(a) and 11(b)). Using the refractive index maps obtained from the Rinck measurements, we simulated the guided modes supported by the waveguide and found perfect agreement with the experimental observations (Figures 11(c) and 11(d)). Simulations were performed using FemSIM™, a modal solution software based on the finite element method (FEM).

[0111] The glass samples were fabricated using Er to design waveguide lasers operating in the C telecommunications band. 3+ , Yb 3+ , and Ce 3+ Doped with Ce 3+ is doped 4I 11 / 2 State Er 3+ and 4F 7 / 2 State Ce 3+ The former radioactive 4I increases the 1.5 μm erbium emission by resonant energy transfer between 13 / 2 →4I 15 / 2 This promotes 1.5 μm emission. Since a large parameter space was explored to create several waveguides, all of which exhibited multimode behavior at 3.5 μm, it became necessary to select the most suitable candidate for laser operation. The 1.5 μm wavelength in these waveguides should be highly multimode, and the use of fiber Bragg gratings in single-mode fiber could result in large coupling losses unless the waveguide-to-fiber transition results in near unity mode overlap between the fiber mode and the fundamental mode of the waveguide (higher-order modes are weakly excited). Therefore, the best parameter to choose would be the insertion loss measured using a multimode fiber close to the laser operating wavelength but outside the absorption band.

[0112] The wavelength for loss measurements was chosen to be 1.62 μm, and the best engraved windows producing low-loss waveguides were those written with a 1 μm pitch, a feed rate between 40 and 150 μ / s, and energies ranging from 2 to 5 μJ. A 12 mm long waveguide written at 40 μ / s with a 1 μm pitch and an energy of 4 μJ exhibited the lowest insertion loss of 0.21 dB / cm.

[0113] This waveguide is incorporated into a laser cavity, the schematic of which is shown in FIG.

[0114] An actual photograph of the setup is shown in Figure 13, highlighting the 980 nm laser pumping waveguide. Green emission is due to the absorption of the excited state of Er. 3+:4S 3 / 2 →4I 15 / 2 Figure 14 shows a laser emission peak centered at 1542.83 nm. In another example using the same configuration, Figure 15 shows a laser emission peak centered at 1561.9 nm.

[0115] Embodiments of the invention described herein provide improved integrated optical elements in fluoride glasses for mid-infrared applications.

[0116] An embodiment of the present invention is an 8×10 -3 and in some embodiments, greater than 2 x 10 -2 This method can be shown to achieve optical waveguides with positive refractive index changes exceeding 100 Å. The refractive index change is primarily due to material densification driven by barium migration in the modified fluoride glass composition. Such strong migration to form optical waveguides has been avoided in the past when waveguides were inscribed with common compositions containing lanthanum fluoride. The modified composition described herein allows for the migration of heavy barium atoms into the positive refractive index zone, which increases and densifies the local refractive index.

[0117] Embodiments of the invention described herein provide improved integrated optical elements in fluoride glasses for visible to mid-infrared applications.

[0118] An embodiment of the present invention is an 8×10 -3 and in some embodiments, greater than 2 x 10 -2 It is shown to achieve optical waveguides with high positive refractive index changes exceeding .gtoreq. ...

[0119] In compliance with the statute, the invention has been described in language specific to more or less structural or systematic features. Terms such as "comprises," "comprising," "consisting of," and variations thereof, are used throughout in an inclusive sense and do not exclude any additional features.

[0120] It is to be understood that the means described herein include preferred forms for putting the invention into effect, and therefore the invention is not limited to the specific features shown or described.

[0121] The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims as appropriately interpreted by those skilled in the art.

Claims

1. a fluoride glass substrate configured to have a concentration of a chemical element of the fluoride glass substrate at an inner contact; a waveguide inscribed in the fluoride glass substrate along a path defined by the inner contacts; The waveguide is 8×10 －３ 1. An optical waveguide device having a positive refractive index contrast exceeding

2. a fluoride glass substrate configured or modified to have a local increase in concentration of a chemical element at the inner contact; a waveguide inscribed in the fluoride glass substrate along a path defined by the inner contacts; The waveguide is 8×10 －３ 1. An optical waveguide device having a positive refractive index contrast exceeding

3. 3. The optical waveguide device according to claim 1, wherein the fluoride glass substrate comprises a composition having amorphous properties.

4. 3. The optical waveguide device of claim 1, wherein the fluoride glass substrate consists primarily of halogen anions with an oxide content of less than 5 mol %.

5. The fluoride glass substrate is ZrF ４ and, BaF ２ , AlF ３ , NaF, ErF ３ , YbF ３ , and CeF ３ and a regulator selected from the group consisting of:

6. 6. The optical waveguide device of claim 1, wherein the fluoride glass substrate is configured to have a concentration of one or more chemical elements at the inner contacts.

7. 7. The optical waveguide device of claim 6, wherein the chemical elements concentrated in the fluoride glass substrate include one or more rare earth elements.

8. 7. The optical waveguide device of claim 6, wherein the chemical elements enriched in the fluoride glass substrate are selected from the alkaline earth group (II) and / or the lanthanide series.

9. 7. The optical waveguide device of claim 6, wherein the chemical elements concentrated in the fluoride glass substrate include one or more of barium, strontium, and calcium.

10. 7. The optical waveguide device of claim 6, wherein the chemical elements concentrated in the fluoride glass substrate include one or more of lanthanum and cerium.

11. 11. The optical waveguide device of claim 1, wherein the fluoride glass substrate comprises elements selected to provide optical gain at one or more wavelengths in the range of 190 nm to 7000 nm.

12. 12. The optical waveguide device of claim 1, wherein the elements selected to achieve optical gain include rare earth elements.

13. The waveguide has a thickness of 1 μm ２ ~2500μm ２ 13. The optical waveguide device of claim 1, having a cross-sectional area in the range of

14. 1. A method for forming an optical waveguide in a fluoride glass substrate, comprising: directing a focused laser pulse into the fluoride glass substrate; Inducing a concentration of a chemical element in the fluoride glass substrate at an internal contact point by scanning the laser pulse across the fluoride glass substrate to inscribe a waveguide in the fluoride glass substrate, and forming a 8×10 －３ and forming a waveguide having a positive refractive index contrast greater than

15. 1. A method for forming an optical waveguide in a fluoride glass substrate, comprising: directing a focused laser pulse into the fluoride glass substrate; and inducing a local increase in the concentration of a chemical element in the fluoride glass substrate at an internal contact point by scanning the laser pulse across the fluoride glass substrate to inscribe a waveguide in the fluoride glass substrate, and inducing a local increase in the concentration of a chemical element in the fluoride glass substrate at an internal contact point, wherein the laser pulse inscribes a waveguide in the fluoride glass substrate. －３ and forming a waveguide having a positive refractive index contrast greater than

16. The method of claim 14 or 15, wherein the laser pulses have a repetition rate in the range of 1 kHz to 200 kHz.

17. The method of claim 14 or 15, wherein the laser pulses have a wavelength in the range of 190 nm to 1600 nm.

18. 18. The method of any one of claims 14 to 17, wherein the laser pulses are scanned across the fluoride glass substrate at a scan speed in the range of 5 micrometers per second to 500 micrometers per second.

19. 19. The method of any one of claims 14 to 18, wherein the laser pulses have an energy per pulse in the range of 100 nJ to 10,000 nJ.

20. 20. The method of any one of claims 14 to 19, wherein the laser pulses have a pulse duration in the range of 10 to 500 femtoseconds.

21. 21. The method of any one of claims 14 to 20, wherein the laser pulses are focused by a focusing device to a diameter of between 250 nm and 50 μm.

22. 22. The method of claim 21, wherein the focusing device comprises one or more of a microscope objective, a lens, and a curved mirror.

23. 23. The method of any one of claims 14 to 22, wherein the waveguide is formed by a single translation of a laser focus.

24. 24. The method of any one of claims 14 to 23, wherein the waveguide is formed by multiple translations of the inner contact, each of the multiple translations separated perpendicular to the direction of translation by between 200 nm and 3500 nm.

25. 25. The method of any one of claims 14 to 24, wherein the laser pulses have an energy per pulse in the range of 2 to 6 μJ.

26. 26. The method of any one of claims 14 to 25, further comprising performing multiple scans with a multiscan pitch of 1 μm.

27. 27. The method of any one of claims 14 to 26, further comprising forming a laser cavity using broadband butt-coupled high reflectivity (HR) mirrors and fiber Bragg gratings positioned at opposite ends of the active waveguide for lasing the waveguide.

28. 1. An optical waveguide device, comprising: a fluoride glass substrate configured with a concentration of a chemical element of the fluoride glass substrate at an interior junction that defines a waveguide path; and a waveguide inscribed in the fluoride glass substrate along the waveguide path, the waveguide having an 8×10 －３ a waveguide having a positive refractive index contrast greater than a mirror disposed at one end of a waveguide formed in a substrate of the optical waveguide device; a grating disposed at an end of the waveguide opposite the mirror.

29. 30. The optical device of claim 28, wherein the mirror is a high reflectivity (HR) mirror.

30. 30. The optical device of claim 28 or 29, wherein the grating comprises an optical grating.

31. 31. The optical device of claim 30, wherein the optical grating is a fiber Bragg grating (FBG).

32. 32. The optical device of any one of claims 28 to 31, further comprising a laser source configured to provide light and / or energy to the optical waveguide device for laser processing.

33. 33. The optical device of any one of claims 28 to 32, wherein the waveguide, the mirror, and the grating form a laser cavity.

34. 29. The optical device of claim 28, wherein the laser is configured with an energy per pulse in the range of 2-6 μJ, a feed rate in the range of 40-150 μm / s, and a multi-scan pitch of 1 μm.

35. a fluoride glass substrate; a waveguide inscribed in the fluoride glass substrate, the waveguide being 8×10 －３ and a waveguide having a positive refractive index contrast greater than

36. A waveguide formed in a fluoride glass substrate, the fluoride glass substrate configured to have a concentration of a chemical element of the fluoride glass substrate at an internal contact to form the waveguide in the fluoride glass substrate, the concentration being 8×10 －３ A waveguide with a positive refractive index contrast exceeding

37. 1. A waveguide formed in a fluoride glass substrate, the fluoride glass substrate being configured or modified to have a local increase in concentration of a chemical element of the fluoride glass substrate at an internal junction to form the waveguide in the fluoride glass substrate, the fluoride glass substrate having a concentration of 8×10 －３ A waveguide with a positive refractive index contrast exceeding

38. a glass substrate configured to have a concentration of a chemical element of the glass substrate at an internal contact; a waveguide inscribed in the glass substrate along a path defined by the internal contacts, the waveguide having an 8×10 －３ and a waveguide having a positive refractive index contrast greater than

39. 39. The optical waveguide device of claim 38, wherein the glass substrate comprises a composition having amorphous properties.

40. 39. The optical waveguide device of claim 38, wherein the glass substrate is a halogen glass substrate.

41. 39. The optical waveguide device of claim 38, wherein the glass substrate consists primarily of halogen anions with an oxide content of less than 5 mole percent.

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