Tunable laser and method for manufacturing the same - Patents.com

Abstract

A linear tunable laser comprising a first tunable resonator, a second tunable resonator, an interferometer, an optical amplifier, and a power splitter. The first tunable resonator includes a waveguide. The interferometer comprises a plurality of waveguides. At least one of the waveguides of the interferometer is optically connected to the first tunable resonator. The optical amplifier is optically connected to the interferometer. The second tunable resonator comprises a waveguide optically connected to the optical amplifier. The power splitter is for outputting light from the linear tunable laser.

Description

[Background technology]

[0001] Tunable lasers are used to generate light of at least one of tunable wavelength and tunable irradiance. This allows for output of light with tuned wavelength and / or irradiance, for example, in communication and optical systems. Efficient output of light and efficient and wide tuning of the output light may allow optical devices to be more precise and / or faster. It would be desirable to provide improved lasers. [Brief description of the drawings]

[0002] [Figure 1] 1 shows a schematic plan view of an example tunable laser. [Diagram 2] 1 shows a schematic plan view of an example tunable laser. [Diagram 3] 1 shows a schematic plan view of an example tunable laser. [Figure 4] 1 shows a schematic plan view of an example tunable laser. [Diagram 5] 1 shows a schematic plan view of an example tunable laser. [Figure 6] 1 shows a schematic plan view of an example tunable laser. [Figure 7] 1 shows a schematic plan view of an example tunable laser. [Figure 8] 1 shows a schematic diagram of a plan view of an example photonic integrated circuit (PIC). [Figure 9] 1 shows a schematic plan view of an example device; [Figure 10] An example manufacturing method is shown diagrammatically. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0003] In the described example, the linear tunable laser is configured such that an optical amplifier amplifies light and an adjustment element, e.g., a tunable resonator or interferometer, to adjust at least one of the irradiance and wavelength of the light output by the tunable laser, such that the tunable laser can provide light of, e.g., a selected wavelength and / or irradiance.

[0004] Examples described herein relate to linearly tunable lasers. Linearly tunable lasers include linear optical cavities, and in some examples, both the wavelength and intensity of the output light from the linearly tunable laser are adjustable. In some examples, the linearly tunable laser is a component of a semiconductor structure, such as a photonic integrated circuit (PIC). The output of light from the linearly tunable laser is for light emitting devices or systems, such as for medical imaging, spectroscopy, telecommunications, optical data transmission, and light detection and ranging (LIDAR).

[0005] In some examples described herein, the output light of the linear tunable laser has a single wavelength intensity peak that is tunable over a range of, for example, more than 35 nanometers. In some examples, the single intensity peak is achieved by a superposition of three optical filters, i.e., a first tunable resonator, a second tunable resonator, and an interferometer. In other examples, the single intensity peak is achieved by a superposition of four optical filters, i.e., a first tunable resonator, a second tunable resonator, a first interferometer, and a second interferometer. In further examples, the single intensity peak and wavelength tuning is achieved by a superposition of two optical filters, i.e., a first tunable resonator and an interferometer, and the tuning of the irradiance of the output light is achieved by the second tunable resonator. In some examples, the single intensity peak and wavelength tuning is achieved by a superposition of two optical filters, i.e., a first tunable resonator and a first interferometer, and the tuning of the irradiance of the output light is achieved by the second tunable resonator and a second interferometer.

[0006] As a general introduction to the examples described herein, referring to FIG. 1, a linear tunable laser 100 includes a first tunable resonator 102 including a waveguide, an interferometer 106 including a plurality of waveguides, at least one of the waveguides being optically connected to the first tunable resonator, an optical amplifier 108 optically connected to the interferometer, a second tunable resonator 116 including a waveguide optically connected to the optical amplifier, and a power splitter 110 for outputting light 112 from the linear tunable laser. The linear tunable laser is configured for outputting light 112. In some examples, the optical connection between the first tunable resonator 102 and the interferometer includes a power splitter 104. In some examples, the optical connection between the second tunable resonator 116 and the optical amplifier 108 includes a power splitter 114. Some such examples are illustrated in FIG. 1, and corresponding reference numbers are provided at the beginning of this paragraph. In some examples, the linear tunable laser comprises a linear cavity, the linear cavity comprising a first tunable resonator, an interferometer, an optical amplifier, a second tunable resonator, and a power splitter. The linear cavity is at least one of a cavity that reduces the footprint of the linear tunable laser and a cavity that achieves more efficient filtering of the lasing mode compared to other cavity configurations, such as a ring-shaped cavity. In some examples, the free spectral range of the first tunable resonator is different from the free spectral range of the second tunable resonator, and in other examples, the free spectral range of the first tunable resonator is the same as the free spectral range of the second tunable resonator. In some examples, the linear tunable laser comprises at least one of an optical input and an optical output. In some examples, the power splitter is a first power splitter, and the linear tunable laser includes a second power splitter for coupling light to the linear tunable laser.

[0007] In some examples, by utilizing wavelength-dependent interference, the interferometer is configured as a spectral filter, which has the effect of suppressing undesired wavelengths of light. In some examples, the interferometer is modulated to allow tuning of the wavelength of light output from the linear tunable laser. In some examples, at least one of the first tunable resonator and the second tunable resonator is configured as a spectral filter, which has the effect of suppressing undesired wavelengths of light. In some examples, spectral filtering of the output light is desirable for applications such as optical communications. This can reduce the need for additional optical components for wavelength tuning, which can, for example, simplify the manufacture of devices including linear tunable lasers, reduce the footprint of devices including lasers, and / or reduce the cost of manufacturing devices including lasers.

[0008] In some examples, by utilizing constructive or destructive interference, at least one of the interferometer, the first tunable resonator, and the second tunable resonator is configured as an intensity modulator to allow modulation of the irradiance of the light output from the linear tunable laser. Output intensity modulation is desirable for applications such as optical coherence tomography or LIDAR. This can reduce the need for additional optical components for output irradiance adjustment, which can, for example, simplify the manufacture of devices including the linear tunable laser, reduce the footprint of devices including the laser, and / or reduce the cost of manufacturing devices including the laser.

[0009] Lasers emit light that is produced by the amplification of light. In some instances, the light emitted from a laser is spatially coherent and temporally coherent.

[0010] The tunable resonator is for forming a standing wave of light by interference. In some examples, the tunable resonator comprises multiple mirrors separated by a distance such that a standing wave is generated when light is injected into the resonator. In some examples, the resonator comprises a ring along which light propagates such that a standing wave is generated when light is injected into the resonator. Other tunable resonators are envisioned, such as plane-parallel resonators, concentric resonators, confocal resonators, disk-shaped resonators, toroidal resonators, or hemispherical resonators. The tunable resonator is tuned by adjusting the optical path length of the resonator, which in turn adjusts the wavelength of the standing wave formed in the resonator. In some examples, tuning the wavelength of the standing wave is achieved by changing the length, circumference, and / or refractive index of the tunable resonator. The refractive index of the tunable resonator is modulated, for example, by an electrorefractive index modulator. In some examples, tuning is achieved by thermal modulation or carrier injection.

[0011] The optical amplifier amplifies the intensity of the optical signal. In some examples, the optical amplification is achieved by at least one of stimulated emission and emission by electron-hole recombination. The wavelength of the light amplified by the optical amplifier is, for example, between 10 nanometers and 1 millimeter. Examples of optical amplifiers are solid-state amplifiers, doped fiber amplifiers, semiconductor amplifiers, Raman amplifiers, or parametric amplifiers. In some examples, the semiconductor amplifiers include indium gallium arsenide phosphide (InGaAsP) or aluminum indium gallium arsenide (AlInGaAs). Other optical amplifiers are contemplated. The power splitter has at least one optical input and splits the light into multiple optical outputs. In some examples, the power splitter is a multimode interferometer (MMI), and in other examples, the power splitter is a beam splitter, a partial mirror, a directional coupler, or a prism, and other power splitters are contemplated. In some examples, the ratio of splitting between the optical outputs of the power splitter is 1:1, although other ratios are contemplated, such as 1:100 to 100:1.

[0012] An interferometer uses interference between multiple light beams when the light beams are mixed. A phase difference between the light beams results in constructive or destructive interference. In some examples, the interferometer is a Mach-Zehnder interferometer, such as an asymmetric Mach-Zehnder interferometer. Other exemplary interferometers are a Fizeau interferometer, a Fabry Perot interferometer, a Michelson interferometer, or a Lyot interferometer, and other interferometers are contemplated. In some examples, the interferometer comprises an electrorefractive modulator. In some such examples, the electrorefractive modulator is configured to modulate the phase difference between the light beams when they interfere.

[0013] A waveguide is for guiding light. Light propagates inside the waveguide and is confined inside the waveguide due to reflections at the boundaries of the waveguide. A waveguide typically has a refractive index higher than the refractive index of the material in contact with the waveguide at the boundaries where light confinement is desired. For example, due to this difference in refractive index at the boundaries where light confinement is desired, total internal reflection occurs when the angle of incidence at those boundaries of the waveguide is greater than the critical angle. In this way, the waveguide guides the propagation of light. For a particular optical mode to propagate in the waveguide, it is desirable for the reflected light at the boundaries of the waveguide to satisfy the conditions for constructive interference. In some examples, the waveguide is at least one of an etched ridge waveguide, a vertical pin junction, and an electrorefractive modulator.

[0014] The optical filter transmits or reflects a first wavelength band of the optical spectrum that has greater irradiance than a second wavelength band of the optical spectrum. The optical filter may be a periodic filter, a bandpass filter, a highpass filter, or a lowpass filter, and other filters are contemplated.

[0015] The optical connections are achieved in various ways in various examples. In some examples, the optical connections are achieved by waveguides, while in other examples other connections such as free space propagation and fiber optic connections are contemplated. In some examples, tapered waveguides connect components requiring different electrical and / or optical properties. In some examples herein, at least one of the optical connections is an optical bond.

[0016] In some examples, the light includes infrared radiation. In some such examples, the wavelength of the light is tunable between 1530 nanometers and 1565 nanometers. In some examples, such wavelengths are used in telecommunications applications.

[0017] The PIC integrates multiple photonic functions, such as, for example, a laser or a photodiode, and other photonic functions are envisioned. In some examples, the PIC is configured for use with at least one of ultraviolet, visible, and infrared light. The optical radiation includes, for example, at least one of ultraviolet, visible, and infrared light. In some examples, the PIC includes electrical circuitry. The PIC is used in communications devices, biomedical devices, and photonic computing, and other applications are envisioned.

[0018] 1, the linear tunable laser 100 includes a first tunable cavity 102, an MMI 104, an interferometer 106, an optical amplifier 108, a power splitter 110, output and / or input light 112, an MMI 114, and a second tunable cavity 116. Optical connections are indicated by lines between the boxes.

[0019] In examples such as that of Figure 2, the interferometer 200 is a first interferometer and the linear tunable laser includes a second interferometer 218 that includes a plurality of waveguides, at least one of which is optically connected to an optical amplifier 208, and at least one of which is optically connected to a second tunable cavity 216. Features of those examples that are similar to those described above are referenced using the same reference numerals incremented by 200 instead of 100, and the corresponding descriptions for such features also apply here.

[0020] In examples such as that of FIG. 3, the first tunable resonator 302 is a tunable ring resonator optically connected by two MMIs 304 to a Mach-Zehnder interferometer comprising two waveguides 316 and 318. In some examples, the Mach-Zehnder interferometer is asymmetric, and in other examples, the Mach-Zehnder interferometer is symmetric. The second tunable resonator is optically connected by two MMIs 314 to a power splitter. In some examples, at least one of the first tunable ring resonator and the second ring resonator comprises a waveguide forming a ring. In some such examples, the waveguide is an electrorefractive modulator. In some examples, the radius of the first tunable resonator is different from the radius of the second tunable resonator, which allows, for example, mode selection. In other examples, the radius of the first tunable ring resonator is the same as the radius of the second ring resonator. Features of those examples that are similar to features described above are referenced using the same reference numerals incremented by 300 instead of 100 or 200, and the corresponding descriptions for such features also apply here.

[0021] In examples such as that of FIG. 4, the second tunable resonator 416 is connected by two MMIs 414 to a Mach-Zehnder interferometer comprising two waveguides 420 and 422. In some such examples, at least one of the waveguides of the Mach-Zehnder interferometer is an electrorefractive modulator. In some examples, the Mach-Zehnder interferometer is asymmetric, and in other examples, the Mach-Zehnder interferometer is symmetric. In the example of FIG. 4, the waveguides of the first tunable resonator 402 and the second tunable resonator 416 are curved to form a tunable ring resonator, but are not circular. In some examples, the first tunable resonator and the first interferometer are configured to adjust the irradiance of the light output from the linear tunable laser. In some examples, the second tunable resonator and the second interferometer are configured to adjust the wavelength of the light output from the linear tunable laser. Features of those examples that are similar to features described above are referenced using the same reference numerals incremented by 400 instead of 100, 200, or 300, and the corresponding descriptions for such features also apply here.

[0022] In examples such as that of Figure 5, the optical amplifier is a first optical amplifier, and the waveguides of the first tunable resonator 502 and the second tunable resonator 516 include a second optical amplifier and a third optical amplifier, respectively. In some examples, this increases the irradiance of the output of the linear tunable laser 500 without having to increase the size or footprint of the linear tunable laser. Features of those examples are similar to those described above and are referenced using the same reference numerals incremented by 500 instead of 100, 200, 300, or 400, and the corresponding descriptions for such features also apply here.

[0023] 6, the first tunable resonator is a disk resonator 626 and the second tunable resonator includes a movable mirror 624. Features of those examples that are similar to features described above are referenced using the same reference numerals incremented by 600 instead of 100, 200, 300, 400, or 500, and the corresponding descriptions for such features also apply here.

[0024] 7, the power splitter is a directional coupler 728 formed by an output waveguide 712 that is optically connected to a linear tunable laser at the junction between the optical amplifier 708 and the second interferometers 720 and 722. Features of those examples are similar to those described above and are referred to using the same reference numerals incremented by 700 instead of 100, 200, 300, 400, 500, or 600, and the corresponding descriptions for such features also apply here.

[0025] Some examples are configured for use with or integration into a common photonic platform, such as an indium phosphide (InP) platform, In some examples, integration into a common photonic platform simplifies the combination of the linear tunable laser with one or more components of a PIC, which may, for example, allow for easier, cheaper, and / or faster manufacturing of the PIC.

[0026] In some examples, such as the example of Figure 8, the linear tunable laser 800 is on a substrate 830, where the substrate is a monolith of a PIC. In other examples, the substrate is not a monolith of a PIC. In some examples, the linear tunable laser is integrated into a PIC.

[0027] In examples, such as the example of Figure 9, the photonic device includes a PIC 930, which includes the tunable linear laser 900 described above, an output of light 934, and an electrical controller 932. In some examples, the controller 932 is configured to adjust at least one of the peak wavelength of the light output from the linear tunable laser and the irradiance of the peak wavelength of the light output from the linear tunable laser. In some examples, the PIC includes electrical circuitry that allows for external control of the components of the PIC by appropriate electrical connections to electrodes or other electrical contacts of the PIC.

[0028] FIG. 10 illustrates a schematic of a method of manufacturing a linear tunable laser according to the above example, the method including providing a first tunable resonator, providing an interferometer having a plurality of waveguides, at least one of the waveguides being optically connected to the first tunable resonator, providing an optical amplifier optically connected to the interferometer, providing a second tunable resonator including a waveguide, the waveguide being optically connected to the optical amplifier, and providing at least one power splitter for outputting light from the linear tunable laser. As one of ordinary skill in the art will appreciate, one or more of the components of the linear tunable laser may be provided during the manufacturing process by forming 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. In some examples, as one of ordinary skill in the art will appreciate, etching techniques are used to remove portions of material as part of the patterning.

[0029] The above examples should be understood as illustrative examples of the invention. Further examples of the invention are envisioned. For example, at least one of the waveguides, optical amplifiers, tunable resonators, interferometers, semiconductors, and substrates described herein include at least one of indium phosphide (InP), gallium arsenide (GaAs), gallium antimonide (GaSb), gallium nitride (GaN), indium gallium arsenide (InGaAs), indium aluminum arsenide (InAlAs), aluminum gallium indium arsenide (InAlGaAs), indium gallium arsenide phosphide (InGaAsP), silicon (Si), silicon nitride (Si3N4), silicon oxide (SiO2), and lithium niobate (LiNbO3), although other semiconductor and photonic materials are envisioned.

[0030] It will be understood that any feature described in connection with any one of the examples may be used alone or in combination with the other features described, and also in combination with one or more other features of any of the examples, or in any other combination of any of the examples. Moreover, equivalents and modifications not described above may be employed without departing from the scope of the appended claims.

Claims

1. 1. A linear tunable laser, comprising: a first tunable resonator including a waveguide; an interferometer comprising a plurality of waveguides, at least one of the waveguides being optically connected to the first tunable resonator; an optical amplifier optically connected to the interferometer; a second tunable resonator including a waveguide optically connected to the optical amplifier; a power splitter for outputting light from the linear tunable laser.

2. 2. The linear tunable laser of claim 1, wherein at least one of the first tunable resonator, the second tunable resonator, and the interferometer are configured to tune the wavelength of the light output by the power splitter.

3. 3. The linear tunable laser of claim 1, wherein at least one of the first tunable resonator, the second tunable resonator, and the interferometer is configured to adjust the irradiance of the light output by the power splitter.

4. 3. The linearly tunable laser of claim 1 or 2, wherein at least one of the waveguides of the first tunable resonator and the waveguides of the second tunable resonator are curved.

5. 3. The linear tunable laser of claim 1, wherein at least one of the first tunable resonator and the second tunable resonator is a tunable ring resonator.

6. 3. The linear tunable laser of claim 1, wherein the first tunable resonator is a first tunable ring resonator and the second tunable resonator is a second tunable ring resonator, and a radius of the first tunable ring resonator is different from a radius of the second tunable ring resonator.

7. 3. The linear tunable laser of claim 1 or 2, wherein at least one of the first tunable resonator, the second tunable resonator and the interferometer comprises an electrorefractive modulator.

8. 3. The linearly tunable laser of claim 1 or 2, wherein the interferometer is at least one of a Mach-Zehnder interferometer and an asymmetric Mach-Zehnder interferometer.

9. 3. The linear tunable laser of claim 1, wherein the optical amplifier is a first optical amplifier, and at least one of the first tunable resonator and the second tunable resonator comprises a second optical amplifier.

10. 3. The linearly tunable laser of claim 1, wherein the interferometer is a first interferometer and the linearly tunable laser comprises a second interferometer comprising a plurality of waveguides, at least one of the waveguides being optically connected to the optical amplifier and at least one of the waveguides being optically connected to the second tunable resonator.

11. 11. The linear tunable laser of claim 10, wherein the first tunable resonator and the first interferometer are configured to adjust an irradiance of a peak irradiance of the light output by the power splitter, and the second tunable resonator and the second interferometer are configured to adjust a wavelength of the light output by the power splitter.

12. 3. The linearly tunable laser of claim 1 or 2, wherein at least one optical connection or the power splitter comprises at least one of a multimode interferometer and a directional coupler.

13. 3. The linear tunable laser of claim 1 or 2, wherein a free spectral range of the first tunable cavity is different from a free spectral range of the second tunable cavity.

14. 3. The linear tunable laser of claim 1, wherein at least one of the first tunable resonator, the second tunable resonator, and the optical amplifier comprises indium phosphide (InP).

15. 3. The linearly tunable laser of claim 1 or 2, wherein the power splitter is a first power splitter and the linearly tunable laser comprises a second power splitter for coupling light into the linearly tunable laser.

16. 3. The linearly tunable laser of claim 1 or 2, wherein the linearly tunable laser is in a monolith of a photonic integrated circuit.

17. A photonic integrated circuit comprising a linear tunable laser according to claim 1 or 2.

18. A device comprising the photonic integrated circuit of claim 17.

19. 20. The device of claim 18, comprising a controller configured to adjust at least one of a peak wavelength of light output from the linear tunable laser and an irradiance of the peak wavelength of the light output from the linear tunable laser.

20. A method for manufacturing a linearly tunable laser according to claim 1 or 2, comprising the steps of: Providing a first tunable resonator; providing an interferometer comprising a plurality of waveguides, at least one of the waveguides optically connected to the first tunable resonator; providing an optical amplifier optically connected to the interferometer; providing a second tunable resonator including a waveguide, the waveguide optically connected to the optical amplifier; providing at least one power splitter to output light from the linear tunable laser.

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