Tunable laser

Abstract

A tunable laser includes a first wafer, a second wafer, and an optical cavity. The first wafer is made of a first semiconductor material. The first wafer supports an optical amplifier and an electro-optic tunable filter. The second wafer is made of a second material different from the first semiconductor material. The second wafer supports a thermally tunable filter. The optical cavity includes the optical amplifier, the electro-optical tunable filter, and the thermally tunable filter.

Description

Background Art

[0001] Tunable lasers are used to generate light of at least one of tunable wavelength or tunable power. Tuning of the wavelength and / or power output by a tunable laser can be used in communication systems and / or optical systems. It is desirable to provide an improved tunable laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0002] Figures 1 to 4 Each schematically shows a plan view of a tunable laser according to an example.

[0003] Figure 5 Schematically illustrated is a plan view of a portion of a photonic integrated circuit (PIC) according to an example.

[0004] Figure 6 A plan view of a device according to an example is schematically shown.

[0005] Figure 7 and Figure 8 Each schematically illustrates a method of manufacturing a tunable laser according to an example. DETAILED DESCRIPTION

[0006] In an example to be described, a tunable laser comprises a first wafer of a first semiconductor material. The first wafer supports an optical amplifier and an electro-optical tunable filter. The tunable laser also comprises a second wafer of a second material, the second material being different from the first semiconductor material. The second wafer supports a thermally tunable filter. The tunable laser comprises an optical cavity comprising an optical amplifier, an electro-optical tunable filter, and a thermally tunable filter. The combined electro-optical tunable filter and the thermally tunable filter are configured to tune at least one of the power or wavelength of light to be output by the tunable laser. In doing so, the tunable laser can, for example, provide an output of a selected wavelength and / or power. The output of the tunable laser is, for example, used in photonic devices or systems, such as those used in medical imaging, spectroscopy, telecommunications, optical data transmission, random number generation, and light detection and ranging (LIDAR).

[0007] At least one of the electro-optical tunable filter or the thermally tunable filter can be configured to suppress unwanted wavelengths of light so that the output of the tunable laser can be switched between different wavelengths. For example, spectral filtering of the output of the tunable laser is required for applications such as communications, spectroscopy, or imaging. This can reduce the need for additional optical components for wavelength tuning, which can simplify the manufacture of devices including the tunable laser, reducing the footprint and / or production cost of the device including the laser.

[0008] At least one of the electro-optical tunable filter or the thermally tunable filter can be configured to modulate the output power of the tunable laser; in such examples, the electrical signal can be directly converted into an optical signal. In some examples, modulating the output power of the tunable laser in response to the electrical signal input to the electrically tunable filter is required for applications such as communications. This can reduce the need for additional optical components for electro-optical modulation, which, for example, simplifies the manufacture of a device including a tunable laser, reduces the footprint and / or production cost of the device including the laser.

[0009] In some examples, the output of the tunable laser has a single wavelength intensity peak that is tunable within a certain range. The range is, for example, in the range of 10 nanometers to 1 millimeter. The single intensity peak and / or wavelength tuning can be achieved by superposition of a thermally tunable filter and an electro-optical tunable filter. In some examples, the light amplified by the optical amplifier is used to amplify infrared; in some such examples, the output wavelength of the tunable laser is tunable between 1530 nanometers and 1565 nanometers. Such wavelengths can be used for telecommunication applications.

[0010] A tunable optical filter is an optical element that can be tuned to adjust its output spectrum (eg, the frequency spectrum of the output). The tunable optical filter may include at least one of a tunable resonator or an interferometer.

[0011] An electro-optic tunable filter is a type of tunable filter. The output spectrum of an electro-optic tunable filter can be tuned by an electro-optic effect such as the Pockels effect or the Kerr effect, where the refractive index of a material depends on the electric field applied to it. An electro-optic tunable filter can be a diode and / or reverse biased. Therefore, an electro-optic tunable filter requires a material that exhibits an electro-optic effect, such as indium phosphide (InP), indium gallium arsenide phosphide (InGaAsP), aluminum gallium arsenide (AlGaAs), lithium niobate (LiNbO3) or beta barium borate (BBO).

[0012] A thermally tunable filter is a type of tunable filter. The output spectrum of a thermally tunable filter can be tuned by the thermo-optic effect. The thermo-optic effect causes the refractive index of a material to depend on the temperature of the material. Therefore, a thermally tunable filter requires a material that exhibits the thermo-optic effect and is mechanically resilient to temperature changes, such as silicon (Si) or silicon nitride (SiN).

[0013] The first semiconductor material is different from the second material. In some such examples, the first semiconductor material exhibits an electro-optic effect and the second material exhibits a thermo-optic effect. The use of such materials can increase the design freedom within the tunable laser, and in some such examples, the tunable laser includes an electro-optic component, a thermo-optic component, an electro-optic tunable filter, and a thermal tunable filter. It has been found that it is desirable that the material used by the electro-optic tunable filter is a material such as a material having an electro-optic effect, and the thermal tunable filter uses a different material, such as a material having a thermo-optic effect. In some examples, the first semiconductor material is InP and the second material is SiN. It should be noted that although in some examples the first semiconductor material may also exhibit a thermo-optic effect to some extent and / or in some examples the second material may also exhibit an electro-optic effect to some extent, the tunable laser in the examples herein is configured not to utilize these effects for tuning. Instead, the laser is configured to use the electro-optic effect of the first semiconductor material and the thermo-optic effect of the second material.

[0014] The terms and features used in this article, such as waveguides, tunable resonators, and interferometers will be described in more detail below. However, it is useful to specify the wafers mentioned in this article: wafers may also be referred to as chips, slices, substrates, or layers. A wafer is, for example, a generally flat or relatively thin portion of a material, and in some examples is crystalline. A wafer can be a crystalline Si wafer or a portion of a wafer for a semiconductor manufacturing plant, and in some such examples is a 125 gram, 300 mm diameter wafer. A wafer may alternatively be a crystalline InP wafer or a portion of a wafer for a semiconductor manufacturing plant, and in some such examples is a 25 mm, 51 mm, 76 mm, 100 mm, 200 mm, or 300 mm diameter wafer.

[0015] Reference now Figure 1 A general introduction is given to the examples herein involving tunable lasers. Figure 1A plan view of a tunable laser 100 is schematically shown. The tunable laser 100 includes a first wafer 102 of a first semiconductor material. The first wafer 102 supports or includes an optical amplifier 104 and an electro-optical tunable filter 106. The tunable laser 100 also includes a second wafer 110 of a second material. The second material is different from the first semiconductor material. The second wafer 110 supports or includes a thermally tunable filter 108. The second wafer 110 is optically connected to the first wafer 102. The tunable laser 100 includes an optical cavity 120. The optical cavity includes: an optical amplifier 104, an electro-optical tunable filter 106, and a thermally tunable filter 108. In addition to the order shown, other orders of elements configured as an optical cavity can also be envisioned. The first wafer 102 is in contact with and abuts the second wafer 110. In other examples not shown, the first wafer is optically connected to the second wafer and is not in contact with the second wafer. In various examples, the first wafer is on the second wafer; the second wafer is on the first wafer; the first wafer supports the second wafer; and / or the second wafer supports the first wafer. Figure 1 In the figures, dashed lines are used to indicate that the first wafer or the second wafer may extend laterally beyond the position shown (eg, as part of a PIC).

[0016] Reference now Figure 2 Other examples involving tunable lasers are described herein. In some examples, the optical cavity is configured as a ring optical cavity, for example, the components in the cavity are optically connected in series to form a ring. Such tunable lasers may be referred to as tunable ring lasers. Tunable ring lasers may be used in ring laser gyroscopes or devices for gravitational waves, relativistic effects, or quantum electrodynamic effects.

[0017] Figure 2 Schematically shows a plan view of an example tunable laser 200 described herein. Figure 2 Features and uses involved Figure 1 Where the features described correspond, the reference numerals used are greater than those used for Figure 1 The corresponding reference numerals are 100 greater (e.g., Figure 1 102 of them are Figure 2 202 in ); the corresponding description of such features also applies here. Figure 1 , dashed lines are used to indicate that the first wafer or the second wafer may extend laterally beyond the location shown (eg, as part of a PIC).

[0018] The optical cavity 220 is configured as a ring optical cavity 220, but other ring optical cavity configurations are contemplated in addition to those shown. The tunable laser 200 includes a first wafer 202 that supports and / or includes an optical amplifier 204 that is optically connected to an electro-optical tunable filter 206 via a first waveguide 215. The tunable laser 200 also includes a second wafer 210 that supports and / or includes a thermally tunable filter 208 that is optically connected to the optical amplifier 204 via a second waveguide 213. The second wafer 210 is optically connected to the first wafer 202 via the second waveguide 213. The thermally tunable filter 208 is optically connected to the electro-optical tunable filter 206 via a third waveguide 211 to form a ring optical cavity 220. The ring optical cavity 220 includes the optical amplifier 204, the electro-optical tunable filter 206, and the thermally tunable filter 208. In addition to the order shown, other orders of elements configured as a ring light cavity are also contemplated.

[0019] Reference now Figure 3 Other examples involving tunable lasers are described herein. In some examples, the optical cavity is a linear optical cavity. Components in the linear optical cavity are optically connected in series with a reflector, a partial reflector, a resonator, and / or an interferometer at each end of the linear optical cavity. Such tunable lasers may be referred to as tunable linear lasers or linear tunable lasers. For example, a linear optical cavity may reduce the footprint of a linear tunable laser and / or achieve more efficient laser mode filtering compared to other cavity configurations such as a ring cavity.

[0020] Figure 3 A plan view of an example tunable laser 300 described herein is schematically shown, wherein the optical cavity 320 is configured as a linear optical cavity 320, although other configurations of the optical cavity are contemplated in addition to the configuration shown. Other orders of elements configured as the optical cavity are contemplated in addition to the order shown. Figure 3 Features and uses involved Figure 1 Where the features described correspond, the reference numerals used are greater than those used for Figure 1 The corresponding reference numerals are 200 greater (e.g., Figure 1 102 of them are Figure 3 302 in ); the corresponding description of such features also applies here. Figure 1 and Figure 2 , dashed lines are used to indicate that the first wafer or the second wafer may extend laterally beyond the location shown (eg, as part of a PIC).

[0021] The tunable laser 300 includes a first wafer 302 that supports and / or includes an optical amplifier 304 that is optically connected to an electro-optical tunable filter 306 via a second waveguide 316. The first wafer 302 also supports and / or includes a resonator 312. In other examples, the resonator is at least one of: a reflector, a partial reflector, or an interferometer. The resonator 312 is optically connected to the optical amplifier 304 via a fourth waveguide 324. The tunable laser 300 also includes a second wafer 310 that supports and / or includes a thermally tunable filter 308 that is optically connected to the electro-optical tunable filter 306 via a first waveguide 314. The second wafer 310 is optically connected to the first wafer 302 via the first waveguide 314. The second wafer 302 also supports and / or includes a multi-mode interferometer (MMI) 318. In other examples, MMI 318 is at least one of a reflector, a partial reflector, a resonator, or another configuration of an interferometer. MMI 318 is optically connected to thermally tunable filter 308 via third waveguide 326. MMI 318 has an output 322, which is the output of tunable laser 300. Linear optical cavity 320 includes resonator 312, optical amplifier 304, electro-optical tunable filter 306, thermally tunable filter 308, and MMI 318.

[0022] Reference now Figure 4 Other examples related to tunable lasers are described herein. Figure 4 Schematically shows a plan view of a tunable laser 400 of an example described herein. Figure 4 Features and uses involved Figure 3 Where the features described correspond, the reference numerals used are greater than those used for Figure 3 The corresponding reference numerals are 100 greater (e.g., Figure 3 The 302 in Figure 4 402 in ); the corresponding description of such features also applies here. Figures 1 to 3, dashed lines are used to indicate that the second wafer may extend laterally beyond the illustrated position (e.g., as part of a PIC). The first wafer 402 is supported by and on the second wafer 410. In other examples not shown, the second wafer is supported by and / or on the first wafer. The tunable laser 400 includes a first wafer 402 that supports and / or includes an optical amplifier 404 that is optically connected to an electro-optical tunable filter 406 via a second waveguide 416. The electro-optical tunable filter 406 includes tunable ring resonators 428 and 430. The tunable ring resonators 428 and 430 of the electro-optical tunable filter 406 are optically connected via at least one MMI and / or at least one waveguide. In other examples not shown, the electro-optical tunable filter includes an interferometer. The tunable laser 400 also includes a second wafer 410 that supports and / or includes a thermally tunable filter 408 that is optically connected to the electro-optical tunable filter 406 via a first waveguide 414. The thermally tunable filter 408 includes a tunable ring resonator 432 and an interferometer 434. In other examples not shown, the thermally tunable filter includes a plurality of tunable ring resonators. The tunable ring resonator 432 is optically connected to the interferometer 434 via at least one MMI and / or at least one waveguide. In various examples, at least one of the electro-optical tunable filter or the thermally tunable filter includes a tunable resonator. The second wafer 402 supports and / or includes a first MMI 418 and a second MMI 436. The first MMI 418 is optically connected to the thermally tunable filter 408 via a third waveguide 426. The second MMI 436 is optically connected to the optical amplifier 404 via the third waveguide 426. The first MMI 418 has an output 422, which is the output of the tunable laser 400. The second wafer 410 is optically connected to the first wafer 402 via the first waveguide 414 and the fourth waveguide 425. The tunable laser 400 includes an optical cavity including: an optical amplifier 404, an electro-optical tunable filter 406, a thermally tunable filter 408, a first MMI 418, and a second MMI 436.

[0023] Reference now Figure 5Examples involving PICs are described herein. A tunable laser may be configured for use with or integrated into a universal photonic platform. In some examples, at least one of the first wafer or the second wafer is a substrate for the PIC; in other examples, the first wafer and the second wafer are supported by and / or are on a substrate for the PIC. The universal photonic platform uses standardized processes to manufacture photonic components and / or standardized photonic components for the resulting PIC. Integration into the universal photonic platform may simplify the combination of the tunable laser with one or more components of the PIC. The tunable laser may be integrated into the universal platform; in some such examples, the PIC is simpler, cheaper, faster to manufacture and has a wide range of applications. The PIC integrates multiple photonic functions, such as a laser or a photodiode, but other photonic functions are also contemplated. In Figure 5 In the example schematically shown in plan view of FIG. , a photonic integrated circuit 540 includes an example tunable laser 500 described herein. Figure 5 Features and uses involved Figure 1 Where the features described correspond, the reference numerals used are greater than those used for Figure 1 The corresponding reference numerals are 400 greater (e.g., Figure 1 102 of them are Figure 5 502); the corresponding description of these features also applies here.

[0024] PIC 540 includes a tunable laser 500 supported by and on a substrate 538. A first wafer 502 and a second wafer 510 of the tunable laser 500 are on the substrate 538, and the substrate 538 is used for the PIC 540. In other examples not shown, the substrate is not used for the PIC, but for example, the substrate is a printed circuit board (PCB), an integrated circuit (IC), or a support for the tunable laser 500. The support for the tunable laser can improve the thermal stability and / or mechanical stability of the laser, which can improve the performance of the tunable laser. In some examples, the tunable laser is integrated into the PIC. Dashed lines are used to indicate that in some examples, the first wafer or the second wafer is part of the substrate. In some examples, the substrate is made of a third material, and in some such examples, the first semiconductor material or the second material is the same as the third material.

[0025] Reference now Figure 6 Examples of devices described herein are described. Some examples herein are directed to devices including the PICs described herein. Figure 6 Schematically, a plan view of at least a portion of a photonic device 642 including a PIC 640 including a tunable laser 600 is shown. Figure 6 Features and uses involved Figure 3 or Figure 5Where the features described correspond, the reference numerals used are greater than those used for Figure 3 or Figure 5 The corresponding reference numerals are respectively 300 or 100 greater (e.g., Figure 3 The 302 in Figure 6 602 of them, and Figure 5 538 of them are Figure 6 638 of ); the corresponding description of these features also applies here.

[0026] The photonic device 642 includes an output for light 622, for example for light emitting applications such as LIDAR. In other examples not shown, the photonic device does not emit light, for example, for a random number generator photonic device, no or less light emitted within the PIC leaves the PIC. The photonic device includes a controller 646 electrically connected to the tunable laser 600 via an electrical connection 648. In some examples, the controller 630 is used for at least one of modulation of the power of the output 622 of the tunable laser 600 or modulation of the peak wavelength of the output 622. The controller 646 can be a control circuit, an IC, a processor, a microcontroller, or a computer. Other controllers are also contemplated. In some examples, the PIC 640 includes circuitry and / or external control of components of the PIC 640 through appropriate electrical connections to electrodes or other electrical contacts on the PIC 640.

[0027] Reference now Figure 7 and Figure 1 Describe the examples described herein (such as Figure 1 Example of method 750 for manufacturing tunable laser 100 ( Figure 1 is used as an example, method 750 can also be applied to Figures 2 to 4 any examples of ). Figure 7A method 750 is schematically shown, and includes providing a first wafer 102 of a first semiconductor material (752). The first wafer 102 supports an optical amplifier 104 and an electro-optical tunable filter 106. Providing the first wafer 102 (752) may include using a pre-assembled, pre-formed, and / or pre-processed wafer. In other examples, providing the first wafer (752) includes assembling, processing, and / or forming the first wafer 102. The method then includes providing a second wafer 110 of a second material that is different from the first semiconductor material (754). The second wafer 110 supports a thermally tunable filter 108. Providing the second wafer 110 (754) may include using a pre-assembled, pre-formed, and / or pre-processed wafer. In other examples, providing the second wafer (754) includes assembling, processing, and / or forming the first wafer. Then, the method includes optically connecting the first wafer 102 to the second wafer 110 (756) so that the optical cavity 120 of the tunable laser 110 includes the optical amplifier 104, the electro-optical tunable filter 106, and the thermally tunable filter 108. Such methods may be referred to as hybrid integration. The first wafer and the second wafer may be optically connected by mechanically connecting the first wafer 102 and the second wafer 104. In other examples, the first wafer and the second wafer are optically connected, and are not mechanically connected and / or in contact. Mechanically connecting the first wafer 102 and the second wafer 110 may include bonding and / or attaching the first wafer 102 directly or indirectly to the second wafer 110. In other examples, mechanically connecting the first wafer 102 to the second wafer 110 includes attaching and / or bonding both the first wafer 102 and the second wafer 110 to a substrate, or in other examples, micro-transfer printing the first wafer on the second wafer, or micro-transfer printing at least one of the first wafer or the second wafer on a substrate. In another example, mechanically connecting the first wafer 102 and the second wafer 110 includes abutting the first wafer 102 and the second wafer 110. Other mechanical connections between the first wafer 102 and the second wafer 110 are also contemplated. Hybrid integration is, for example, providing a first wafer 102 supporting a photonic component and a second wafer 110 supporting a photonic component when manufacturing a tunable laser 100, a PIC, or a photonic device, and then optically connecting the first wafer 102 and the second wafer 110 to each other. Hybrid integration may include processes and / or techniques for providing a first wafer 102 or a photonic component supported by the first wafer 102 that is incompatible with the second wafer 110 or the photonic component supported by the second wafer. Hybrid integration may include processes and / or techniques for providing a second wafer 110 or a photonic component supported by the second wafer 110 that is incompatible with the first wafer 102 or the photonic component supported by the first wafer 102.In some examples of hybrid integration, providing the first wafer 102 (752) supporting the optical amplifier 104 and the electro-optical tunable filter 106 and providing the second wafer 110 (754) supporting the thermally tunable filter 108 are completed at different times by different parties or in different geographical locations. Some examples herein relate to a method of manufacturing a PIC, which includes the method 750 of manufacturing a tunable laser 100 as described herein. In addition, some examples herein relate to a method of manufacturing a device, which includes the method 750 of manufacturing a tunable laser 100 as described herein or the method of manufacturing a PIC as described herein.

[0028] Reference now Figure 8 and Figure 1 Describe the examples described herein (such as Figure 1 Another example of method 860 of manufacturing tunable laser 100 ( Figure 1 is used as an example, method 750 can also be applied to Figures 2 to 4 any examples of ). Figure 8 A method 860 is schematically illustrated and includes providing a first wafer 102 of a first semiconductor material (862). Providing the first wafer 102 (862) may include using a preassembled, preformed, and / or preprocessed wafer. In other examples, providing the first wafer 102 (862) includes assembling, processing, and / or forming the first wafer 102. The method then includes providing a second wafer 110 of a second material (864). Providing the second wafer 110 (864) may include using a preassembled, preformed, and / or preprocessed wafer. In other examples, providing the second wafer 110 (864) includes assembling, processing, and / or forming the second wafer 110. The method then includes mechanically coupling the first wafer 102 to the second wafer 110 (866). Similar to the method for Figure 7As described, mechanically connecting the first wafer 102 and the second wafer 110 may include directly bonding and / or attaching the first wafer 102 to the second wafer 110. In other examples, mechanically connecting the first wafer 102 and the second wafer 110 includes attaching and / or bonding both the first wafer 102 and the second wafer 110 to a substrate. In further examples, mechanically connecting the first wafer 102 and the second wafer 110 includes abutting the first wafer 102 and the second wafer 110. Other mechanical connections between the first wafer 102 and the second wafer 110 are also contemplated. Next, the method includes forming the electro-optical tunable filter 106 and the optical amplifier 104 on the first wafer 102, and forming the thermally tunable filter 108 on the second wafer 110 (868), such that the optical cavity 120 of the tunable laser 100 includes the optical amplifier 104, the electro-optical tunable filter 104, and the thermally tunable filter 108. The optical cavity 120 can be configured by optically connecting the first wafer 102 and the second wafer 110 to each other. Heterogeneous integration is, for example, mechanically connecting the first wafer 102 and the second wafer 110 when manufacturing the tunable laser 100, PIC, or photonic device, and then using processes and / or techniques to provide the desired photonic components supported by the first wafer 102 and / or the second wafer 110. Heterogeneous integration may include using a single die and / or a common platform to provide the tunable laser 110, PIC, or photonic device. Heterogeneous integration may reduce the casting time required to produce the tunable laser and / or the footprint of the tunable laser 100. Some examples herein relate to a method of manufacturing a PIC, which includes a method 860 of manufacturing a tunable laser 100 as described herein. In addition, some examples herein relate to a method of manufacturing a device, which includes a method 860 of manufacturing a tunable laser 100 as described herein or a method of manufacturing a PIC as described herein.

[0029] Example methods described herein may include providing a controller as described above. The controller is, for example, configured for at least one of modulation of the power of the output of the tunable laser or modulation of the peak wavelength of the output.

[0030] As will be appreciated by those skilled in the art, one or more of the first wafer, the second wafer, or the components of the tunable laser may be provided by forming them during the manufacturing process using known techniques, such as: metal organic vapor phase epitaxy (MOVPE), surface passivation, photolithography, ion implantation, etching, dry etching, ion etching, wet etching, buffered oxide etching, plasma ashing, plasma etching, heat treatment, annealing, thermal oxidation, chemical vapor deposition, atomic layer deposition, physical vapor deposition, molecular beam epitaxy, laser lift-off, electrochemical deposition, electroplating, or chemical mechanical polishing. As will be appreciated by those skilled in the art, in some examples, etching techniques are used to remove portions of material as part of patterning. Those skilled in the art will appreciate that the first wafer and the second wafer may be mechanically and / or optically connected using known techniques, such as: wafer fusion, anodic bonding, bonding. Those skilled in the art will readily appreciate how to form an optical amplifier, an electro-optical tunable filter, or a thermally tunable filter on the surface of a wafer.

[0031] Some of the terms and features used previously are now described to detail the features of the examples described herein.

[0032] The waveguide herein is used to guide light. Due to reflection at the boundary of the waveguide, the light propagates within the waveguide and is confined within the waveguide. The refractive index of the waveguide is generally greater than the refractive index of the material in contact with the waveguide at the boundary where the light is desired to be guided. In this way, the waveguide guides the propagation of light. In order for light to propagate in the waveguide, it is desired that the light reflected at the boundary of the waveguide satisfies the condition of constructive interference. In some examples, the waveguide is at least one of the following: a semiconductor junction or an electrorefractive modulator.

[0033] The optical amplifier is used to increase the output power of the tunable laser by amplifying the light in the optical cavity. In some examples, the light emitted from the tunable laser is spatially coherent and temporally coherent. In some examples, the light amplification is achieved by at least one of stimulated emission or spontaneous emission caused by electron-hole recombination. The wavelength of the light amplified by the optical amplifier may be between 10 nanometers and 1 millimeter. Examples of optical amplifiers include: solid-state amplifiers, doped fiber amplifiers, semiconductor amplifiers, Raman amplifiers, or parametric amplifiers. The optical amplifier may include InGaAsP or aluminum indium gallium arsenide (AlInGaAs). Other optical amplifiers are also conceivable. The optical amplifier may include an alloy of a first semiconductor material, for example, the optical amplifier includes InGaAsP and the first semiconductor material is InP. This can simplify the integration of the optical amplifier into the first wafer of the tunable laser, provide a first wafer including the optical amplifier, and / or form the optical amplifier on the first wafer.

[0034] A resonator, a reflector, a partial reflector, or an interferometer may be used to provide at least one end of the optical cavity. The reflector may be a mirror. The resonator may be a ring resonator. The interferometer may be an MMI. In some examples, the resonator comprises a ring along the circumference of which the light propagates, the circumference of which is such that a standing wave occurs when the light is injected into the resonator. Other tunable resonators are also contemplated, such as a plane parallel resonator, a concentric resonator, a confocal resonator, a disk resonator, a ring resonator, or a hemispherical resonator.

[0035] A tunable resonator is a structure configured to interfere with an optical mode within the tunable resonator, thereby generating constructive or destructive interference according to one or more effective path lengths and / or wavelengths of one or more modes within the structure. In some examples, the tunable resonator is a tunable ring resonator and includes a ring waveguide structure. The tunable ring resonator may include two waveguides, each waveguide having a first end optically connected to a first power coupler and a second end optically connected to a second power coupler (the power coupler is, for example, an MMI) to form a ring. For example, the radius of the tunable ring resonator may be selected for mode selection. The waveguide of the tunable ring resonator may be bent to form a ring, and in some such examples, the tunable ring resonator is not circular. By tuning the optical path length or refractive index within the resonator, the wavelength of the output spectrum of the tunable resonator is tuned.

[0036] Interferometers are used to interfere with multiple optical modes. The phase difference between the optical modes produces constructive interference or destructive interference. In some examples, the interferometer is a Mach-Zehnder interferometer (MZI), such as an asymmetric MZI (AMZI). Other exemplary interferometers are Fizeau interferometers, Fabry-Perot interferometers, Michelson interferometers, or Lyot interferometers, and other interferometers are also contemplated. The phase difference between the optical modes can be tuned by tuning the optical path length or refractive index within the interferometer, thereby tuning the wavelength of constructive or destructive interference in the interferometer, which in turn tunes the output spectrum and / or power of the interferometer.

[0037] The free spectral range of the tunable filter is the wavelength interval between two continuous reflection or transmission power maxima of the tunable filter. In some examples, the free spectral range of the electro-optical tunable filter is different from the free spectral range of the thermal tunable filter, and in other examples, the free spectral range of the electro-optical tunable filter is the same as the free spectral range of the thermal tunable filter. In some examples where there is a difference between the free spectral range of the electro-optical tunable filter and the free spectral range of the thermal tunable filter, the output of the tunable laser may have a reduced line width. The line width here is the full width at half maximum (FWHM) of the tunable laser output spectrum peak. The line width is, for example, at least one of the following: less than 100 kHz, less than 50 kHz, less than 20 kHz, less than 10 kHz or less than 2 kHz.

[0038] The scanning speed of the tunable filter is the maximum rate at which the peak transmission wavelength of the tunable filter can be tuned, for example in nanometers per second. In some examples, the scanning speed of the electro-optical tunable filter is different from the scanning speed of the thermal tunable filter, and in other examples, the scanning speed of the electro-optical tunable filter is the same as the scanning speed of the thermal tunable filter. In some examples, the electro-optical tunable filter is used to modulate the wavelength of the output of the tunable laser. The scanning speed of the electro-optical tunable filter can be faster than the scanning speed of the thermal tunable filter, for example, because electro-optical tuning requires less heat dissipation than thermal optical tuning. The faster scanning speed of the electro-optical tunable filter can be used, for example, for imaging or telecommunication applications. In some examples, the scanning speed of the electro-optical tunable filter is at least one of 100 times, 1000 times, 10000 times, 100000 times, or 1000000 times the scanning speed of the thermal tunable filter. Compared to thermo-optical tuning, electro-optical tuning may require less electrical power, for example, for low-power devices or applications.

[0039] Low resonant FWHM may be provided by a thermally tunable filter, and / or fast modulation may be provided by an electro-optical tunable filter. An optical cavity is an arrangement of optical elements as cavity resonators for forming standing waves. An optical cavity may be provided by optically connecting an optical amplifier, an electro-optical tunable filter, and a thermally tunable filter. The optical cavity includes an optical amplifier, an electro-optical tunable filter, and a thermally tunable filter.

[0040] Optically connected means, for example, that the optically connected optical elements are configured such that light can propagate through free space between the optically connected optical elements and / or that the optically connected optical elements are optically connected via a waveguide such that light can propagate through a waveguide between the optically connected optical elements. For example, a first wafer and a second wafer are optically connected via an optical element on the first wafer that is optically connected to an optical element on the second wafer. As will be understood by those skilled in the art, optical as used herein refers to at least one of ultraviolet light, visible light, mid-infrared light, C-band infrared light, or infrared light.

[0041] Reference herein to a wafer is, for example, a single layer of the same homogeneous material, but for other examples, it is contemplated that the wafer instead includes one or more layers or portions, each of which is deposited or formed independently of one another (e.g., forming a stack of sub-layers one after another during a manufacturing process, which sub-layers together can be considered a wafer). The wafer may include portions of different materials, for example, for manufacturing. In some examples, at least one of the optical amplifier or the electro-optical tunable filter includes InGaAsP. In some examples, at least one of the electro-optical tunable filter and the optical amplifier includes a first semiconductor material, or the thermally tunable filter includes a second material. In some examples, at least one of the second material or the third material described herein includes at least one of a semiconductor, a dielectric, or a polymer. In various examples, at least one of the first semiconductor material, the second material, or the third material described herein includes at least one of Si, InP, gallium arsenide (GaAs), gallium antimonide (GaSb), gallium nitride (GaN), indium gallium arsenide (InGaAs), indium aluminum arsenide (InAlAs), indium aluminum gallium arsenide (InAlGaAs), AlGaAs, InGaAsP, SiN, silicon oxide (SiO2), tantalum pentoxide (Ta2O5 or tantalum), aluminum oxide (Al2O3 or aluminum oxide), aluminum nitride (AlN), or LiNbO3. Other materials are contemplated in other examples.

[0042] It should be understood that any feature described with respect to any example can be used alone or in combination with other features described, and can also be used in combination with one or more features of any other example, or in combination with any combination of any other example. In addition, equivalents and modifications not described above may also be adopted without departing from the scope of the appended claims.

Claims

1. A tunable laser, comprising: a first wafer of a first semiconductor material, the first wafer supporting an optical amplifier and an electro-optical tunable filter; as well as a second wafer of a second material, the second material being different from the first semiconductor material, the second wafer supporting a thermally tunable filter, An optical cavity includes the optical amplifier, the electro-optical tunable filter and the thermally tunable filter.

2. The tunable laser according to claim 1, wherein: At least one of the following conditions exists: The first wafer is adjacent to the second wafer; The first wafer is on the second wafer; The first wafer supports the second wafer; or The second wafer supports the first wafer.

3. The tunable laser according to claim 1 or claim 2, wherein: At least one of the following conditions exists: The electro-optical tunable filter, or The thermally tunable filter, Includes a tunable resonator.

4. A tunable laser as claimed in any preceding claim, wherein: At least one of the following conditions exists: The electro-optical tunable filter, or The thermally tunable filter, Including interferometer.

5. A tunable laser as claimed in any preceding claim, wherein: At least one of the following conditions exists: The electro-optical tunable filter, or The thermally tunable filter, Includes interferometers and tunable resonators.

6. A tunable laser as claimed in any preceding claim, wherein: The scanning speed of the electro-optical tunable filter is at least 1000 times the scanning speed of the thermally tunable filter, and the wavelength tuning range of the thermally tunable filter is 10 times the wavelength tuning range of the electro-optical tunable filter.

7. A tunable laser as claimed in any preceding claim, wherein: The free spectral range of the electro-optical tunable filter is different from the free spectral range of the thermally tunable filter.

8. A tunable laser as claimed in any preceding claim, wherein: At least one of the following conditions exists: The first semiconductor material includes indium phosphide, or the second material includes silicon.

9. A tunable laser as claimed in any preceding claim, wherein: The optical cavity is a linear optical cavity.

10. A tunable laser as claimed in any preceding claim, wherein: The first wafer or the second wafer is a substrate for a photonic integrated circuit, or the first wafer and the second wafer are supported by a substrate for a photonic integrated circuit.

11. A tunable laser as claimed in any preceding claim, wherein: At least one of the following conditions exists: The electro-optical tunable filter and the optical amplifier comprise the first semiconductor material, or The thermally tunable filter includes the second material.

12. A photonic integrated circuit comprising a tunable laser as claimed in any preceding claim.

13. A device comprising the photonic integrated circuit according to claim 12.

14. The device of claim 13, comprising a controller configured for at least one of modulation of the power of the output of the tunable laser or modulation of the peak wavelength of the output.

15. A method for manufacturing a tunable laser as claimed in any one of claims 1 to 11, the method comprising: providing said first wafer of said first semiconductor material, said first wafer supporting said optical amplifier and said electro-optical tunable filter; providing said second wafer of said second material, said second wafer supporting said thermally tunable filter; The first wafer is optically connected to the second wafer such that the optical cavity of the tunable laser includes the optical amplifier, the electro-optical tunable filter, and the thermally tunable filter.

16. A method for manufacturing a tunable laser as claimed in any one of claims 1 to 11, the method comprising: providing the first wafer of the first semiconductor material; providing the second wafer of the second material; mechanically coupling the first wafer to the second wafer; as well as The electro-optical tunable filter and the optical amplifier supported by the first wafer are formed, and the thermally tunable filter supported by the second wafer is formed, so that the optical cavity of the tunable laser includes the optical amplifier, the electro-optical tunable filter and the thermally tunable filter.

17. A method of manufacturing a photonic integrated circuit comprising the method of claim 15 or claim 16.

18. A method of manufacturing a device comprising the method according to any one of claims 15 to 17.

19. The method of claim 18, comprising providing a controller configured for at least one of modulation of the power of the output of the tunable laser or modulation of the peak wavelength of the output.

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