CN112928599B - Single-chip integrated mode-tunable chaotic laser and manufacturing and control method thereof - Google Patents

Single-chip integrated mode-tunable chaotic laser and manufacturing and control method thereof Download PDF

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CN112928599B
CN112928599B CN202110169286.6A CN202110169286A CN112928599B CN 112928599 B CN112928599 B CN 112928599B CN 202110169286 A CN202110169286 A CN 202110169286A CN 112928599 B CN112928599 B CN 112928599B
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sampling
bragg
mode
grating
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CN112928599A (en
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何扬
施跃春
李密
陈向飞
张学进
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Nanjing University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/065—Mode locking; Mode suppression; Mode selection ; Self pulsating
    • H01S5/0651—Mode control
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/124—Geodesic lenses or integrated gratings
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/13—Integrated optical circuits characterised by the manufacturing method
    • G02B6/138—Integrated optical circuits characterised by the manufacturing method by using polymerisation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
    • H01S5/0085—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for modulating the output, i.e. the laser beam is modulated outside the laser cavity
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/026—Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/026—Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers
    • H01S5/0268—Integrated waveguide grating router, e.g. emission of a multi-wavelength laser array is combined by a "dragon router"
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/065—Mode locking; Mode suppression; Mode selection ; Self pulsating
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/068—Stabilisation of laser output parameters

Abstract

The invention discloses a monolithic integrated mode-tunable chaotic laser and a manufacturing and control method thereof, wherein the laser comprises a left section and a right section of same active equivalent pi phase shift uniform Bragg sampling grating and a middle section of active equivalent pi phase shift antisymmetric Bragg sampling grating which are integrated on the same chip and share a section of optical waveguide; the antisymmetric Bragg sampling grating is used for realizing incident light and reflected light in TE0And TE1Conversion between modes; by respectively adjusting the bias current of the left and right equivalent pi phase shift uniform Bragg sampling gratings, the power ratio of input light and output light injected into the antisymmetric Bragg sampling grating in the middle section is changed, and chaotic laser output is generated. The chaotic laser solves the problem that the mode tunable chaotic laser cannot be realized in the prior art.

Description

Single-chip integrated mode-tunable chaotic laser and manufacturing and control method thereof
Technical Field
The invention relates to the technical field of laser, in particular to a single-chip integrated chaotic laser with tunable mode and a manufacturing and control method of the laser.
Background
The chaotic laser is a special output form of the laser, has the characteristic of wide spectrum similar to noise, and naturally has hiding property and strong applicability. In recent years, with the gradual establishment and improvement of a chaotic laser theory system, the development and application of chaotic laser become research hotspots. The semiconductor laser has the advantages of small volume, low cost, high reliability, easy integration, direct modulation and the like, becomes an advantageous laser device generated by chaotic laser, and is widely applied to the aspects of secret communication, laser ranging, outage detection and the like. A Distributed Feedback (DFB) laser is used as one of semiconductor lasers, a Bragg grating is arranged in the DFB laser, the DFB laser has the advantages of capability of realizing dynamic single longitudinal mode narrow linewidth output, good wavelength stability, good dynamic spectral line and the like, and is a preferred optical device generated by chaotic excitation.
Various integrated chaotic laser chips have been proposed in the prior art, such as: the chaotic chip developed by Athens university in Greece and the Argyris, Froun Hough Telecommunications institute of technology, Heinriches-Hertz, Germany, is composed of four parts, namely a DFB laser source, a gain/absorption region, a phase control region and a feedback cavity [ Physical Review Letters,100(19):194101,2008 ]. An integrated multi-cavity semiconductor laser chip with three external cavities, developed by Tronecu et al, university of Baliazu, Spain [ IEEE Journal of Quantum Electronics,46(12): 1840-. An integrated chaotic chip developed by Japan Saitama Jade university and Sunada et al, NTT communication science laboratory comprises a DFB laser, two independent semiconductor optical amplifiers, a ring-shaped passive optical waveguide and a fast photodetector [ Optics Express,19(7): 5713-.
There are also related reports on forming chaotic laser source by light set in China. Such as: a three-section integrated chaotic chip developed by semiconductor institute of Chinese academy of sciences such as Zhao Dianjuan and Xinan university such as Charlotron consists of three parts, namely a DFB laser region, a phase region and an amplification region [ Optics Express,21(10):23358-23364,2013 ]. An integrated short-cavity chaotic semiconductor laser proposed by Zhang Mingjiang, Tai Yuan Physician university is composed of a distributed feedback laser, a collimating lens, a half-transmitting and half-reflecting mirror, a coupling lens and a passive fiber [ IEEE Photonics Technology Letter,29(12): 1911-. A photonic integrated double-region chaotic semiconductor laser chip (CN20190620624.6) is provided by Lipu et al of Taiyuan university, which is characterized in that a main distributed feedback laser and a secondary distributed feedback laser are integrated on the same chip substrate, and bias current is respectively applied to the two lasers to enable the two lasers to emit light and inject the light into the opposite laser to disturb the light field of the two lasers, thereby generating chaotic laser with high bandwidth and no time delay characteristic.
However, the above schemes all generate chaotic laser in a single mode, and it is desired to realize mode tunability, only a mode converter can be used, and a monolithically integrated mode tunable chaotic laser cannot be realized, which will greatly limit the application of chaotic laser.
Disclosure of Invention
The invention provides a single-chip integrated mode tunable chaotic laser and a manufacturing and control method thereof, which solve the problem that the prior art can not realize the mode tunable chaotic laser.
In order to solve the problems, the invention is realized as follows:
the application provides a single-chip integrated mode-tunable chaotic laser, which comprises a left active equivalent pi phase shift uniform Bragg sampling grating and a right active equivalent pi phase shift antisymmetric Bragg sampling grating which are the same in the left section and the right section, wherein the three sections of the sampling gratings are respectively provided with an independent power supply electrode and are integrated on the same chip and share a section of optical waveguide. The antisymmetric Bragg sampling grating is used for realizing incident light and reflected light in TE0And TE1Conversion between modes, e.g. TE for a forward wave propagating in an antisymmetric Bragg-sampled grating0The mode light is reflected back to TE1Light of a mode. By respectively adjusting the bias current of the left and right equivalent pi phase shift uniform Bragg sampling gratings, the power ratio of input light and output light injected into the antisymmetric Bragg sampling grating in the middle section is changed, chaotic laser output is generated, and the mode switching of chaotic laser can be realized under the condition of certain bias current.
In an equivalent pi-phase shifted antisymmetric Bragg sampled grating, TE0Mode and TE1Mode conversion, forward TE of transmission0TE whose mode will reflect as backward1Mode, equivalently, forward TE of transport1TE whose mode will reflect as backward0Mode(s). Preferably, the bias current makes the end face of the equivalent pi phase shift uniform Bragg sampling grating output light in TE0Mode dominated, or TE1The mode is the main mode.
Preferably, the structure of the equivalent pi-phase shift antisymmetric bragg sampling grating is as follows: the basic sampling grating is an antisymmetric sampling grating, namely, in the transverse direction of the waveguide, the upper and lower lines of uniform sampling gratings with the same sampling grating period have pi phase difference by taking a central axis as a boundary; and a pi phase shift structure is also introduced in the middle of the basic sampling grating along the length direction.
In one embodiment of the present application, the Bragg wavelength is 1550nm, the equivalent pi-phase shifted uniform Bragg sampling grating length is 300 μm, the equivalent pi-phase shifted antisymmetric Bragg sampling grating length is 400 μm, and the waveguide width is 4 μm.
Further preferably, the optical waveguide in the embodiment of the present application is made of an SiO material; the substrate adopts at least one of the following materials: indium phosphide (InP), gallium arsenide (GaAs), silicon (Si).
Further preferably, the embodiment of the present application adopts an inalgas multiple quantum well structure.
In one embodiment of the present application, the equivalent pi phase shift is implemented by changing one sampling period in the central portion of the bragg-sampled grating to 1.5 times the sampling period in other portions.
The application also provides a method for manufacturing the monolithic integrated mode-tunable chaotic laser, which is used for manufacturing the laser in any embodiment of the application and comprises the following steps:
manufacturing a sampling pattern based on a reconstruction-equivalent chirp technology on a photoetching plate to form a mask plate;
forming a uniform seed grating structure on the photoresist covering the wafer by using a holographic exposure technology;
and manufacturing the sampling structure on photoresist by using the mask plate, and forming an equivalent grating structure on the wafer after etching.
The application also provides a control method of the monolithic integrated mode-tunable chaotic laser, which is used for adjusting the laser in any embodiment of the application and comprises the following steps:
applying different bias currents to the left and right active equivalent pi phase shift uniform Bragg sampling gratings to generate input light which disturbs the optical field of the equivalent pi phase shift antisymmetric Bragg sampling grating to generate TE with larger output power0Or TE1Chaotic light with dominant mode.
Further, there are two sections of the left and rightSource equivalent pi phase shift uniform Bragg sampling grating bias current to output light from TE0Mode dominated chaotic light change to TE1Chaotic light with dominant mode, or slave TE1Mode dominated chaotic light change to TE0Chaotic light with dominant pattern, as shown in fig. 5.
The beneficial effects of the invention include:
firstly, the method comprises the following steps: by adjusting the bias current of the three sections of gratings, the frequency detuning amount and the injection intensity ratio of the antisymmetric grating injected into the middle section can be simultaneously adjusted, the optical field of the antisymmetric grating is disturbed to generate chaotic laser, and the output laser mode can be selected, so that the mode tunable chaotic laser is realized.
Secondly, the method comprises the following steps: the technical scheme is that the chaotic laser is generated by utilizing the principle of mutual injection disturbance, and the finally generated chaotic laser has flat frequency spectrum, high bandwidth and no time delay characteristic.
Thirdly, the method comprises the following steps: the grating structure of the technical scheme is of a three-section type, the mode tunable chaotic laser can be generated only by using three sections of Bragg sampling gratings, a phase area and a gain area are not needed, the structure is simpler, and the energy consumption is lower.
Fourthly: the technical scheme is photon integrated, has stable output and is more beneficial to the practicability of chaotic laser.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a grating structure diagram of a monolithically integrated mode tunable chaotic laser chip;
FIG. 2 is a schematic diagram of mode selection;
FIG. 3 is a schematic structural diagram of a monolithically integrated mode-tunable chaotic laser chip material;
FIG. 4 is a schematic diagram of holographic exposure for making a sampled Bragg grating;
FIG. 5 is a chaotic timing diagram for mode switching;
FIG. 6 shows (a) TE0And (b) TE1The power profile of the antisymmetric bragg grating upon incidence of the mode light;
FIG. 7 shows the output TE as the injected power varies1A bifurcation pattern of the pattern chaotic light;
in fig. 4: 101: an N electrode; 102: a substrate; 103: a lower confinement layer; 104: a multiple quantum well active layer; 105: an upper confinement layer; 106: a grating structure layer; 107: a waveguide layer; 108: a P electrode; 109: an insulating layer; 110: electrically isolating the tank.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the specific embodiments of the present invention and the accompanying drawings. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to solve the technical problem that the monolithic integration chaotic laser does not have a mode tunable function, the invention aims to provide a monolithic integration mode tunable chaotic laser, which increases the utilization rate of a mode and provides a mode tunable chaotic laser with low cost, easy packaging and large-scale integration for the future Mode Division Multiplexing (MDM) market of optical communication and laser radar.
In the application, the laser grating is made of a left and a right two sections of same active equivalent pi phase shift uniform Bragg sampling gratings and an active equivalent pi phase shift antisymmetric Bragg sampling grating in a middle section. The ratio of the power of disturbance light injected into the middle section antisymmetric sampling grating to the power of output light of the middle section grating is changed by respectively adjusting the bias current of the left and right sections of equivalent pi phase shift uniform Bragg sampling gratings, chaotic laser is easier to generate, and meanwhile, a mode of the middle section antisymmetric sampling grating for outputting the chaotic laser is selected, and finally chaotic laser with tunable output mode is realized.
The technical solutions provided by the embodiments of the present invention are described in detail below with reference to the accompanying drawings.
Fig. 1 is a grating structure diagram of a monolithically integrated mode-tunable chaotic laser chip.
In the monolithically integrated mode-tunable chaotic laser chip, a substrate is made of one of indium phosphide (InP), gallium arsenide (GaAs) and silicon (Si).
The laser grating part adopts a left and a right two sections of same active equivalent pi phase shift uniform Bragg sampling gratings and an intermediate active equivalent pi phase shift antisymmetric Bragg sampling grating (a first section, a second section and a third section from left to right as shown in FIG. 1). The three sections of sampling gratings are respectively provided with independent power supply electrodes, are integrated on the same chip and share a section of optical waveguide. For example, all three regions are integrated on the same InP epitaxial wafer in a serial manner and share the same optical waveguide; the three areas are electrically isolated and can be respectively powered up.
The equivalent pi phase shift antisymmetric Bragg sampling grating structure is as follows: the basic sampling grating is an antisymmetric sampling grating, namely, in the transverse direction of the waveguide, the central axis is used as a boundary, the integral pi phase difference exists between the upper and lower rows of uniform sampling gratings with the same sampling grating period, a pi phase shift structure is introduced into the middle part of the sampling grating, and the antisymmetric sampling pi phase shift is overprinted on the antisymmetric basic sampling grating, so that the equivalent pi phase shift antisymmetric Bragg sampling grating is formed.
The antisymmetric Bragg sampling grating is used for realizing incident light and reflected light in TE0And TE1Conversion between modes, e.g. TE for a forward wave propagating in an antisymmetric Bragg-sampled grating0The mode light is reflected back to TE1Light of a mode. By respectively adjusting the bias current of the left and right equivalent pi phase shift uniform Bragg sampling gratings, the power ratio of input light and output light injected into the antisymmetric Bragg sampling grating at the middle section is changed to generate chaotic laser output, and the mode switching of the chaotic laser can be realized under the condition of certain bias current, wherein the input light is the light excited after the first section of uniform Bragg sampling grating is electrified, and the output light is the light excited after the second section of uniform Bragg sampling grating is electrifiedThe antisymmetric Bragg sampling grating is used for exciting light after being electrified (the input light and the output light are shown in a figure 2).
By changing the bias current of the equivalent pi phase shift uniform Bragg sampling grating at two ends, only TE on the right end face of the structure can be realized0Mode light emission or TE only1And emitting light of the mode to realize mode switching.
For example, in one embodiment of the present application, the grating structure of the monolithically integrated mode-tunable chaotic laser chip is formed by two identical equivalent pi-phase shift uniform bragg sampling gratings on the left and right and an equivalent pi-phase shift antisymmetric bragg sampling grating on the middle, and the three parts are integrated on one identical lnP chip and share one waveguide. The laser has the same material epitaxial structure, including: the device comprises an n-type substrate, an n-type buffer layer, a waveguide layer, a strain multi-quantum well layer, a grating material layer, a p-type waveguide layer, a p-type limiting layer, an insulating layer and positive and negative electrodes. The equivalent pi phase shift bragg sampled grating of the active region is a sampled grating designed using a reconstruction-equivalent chirp technique.
In specific implementation, the chip substrate is an In-P substrate, and the optical waveguide is made of SiO2The material, the laser adopts InAlGaAs multiple quantum well structure, wherein the equivalent pi phase shift uniform Bragg sampling grating length of both ends is 300 μm, the equivalent pi phase shift antisymmetric Bragg sampling grating length of the middle section is 400 μm, and the Bragg wavelength is around 1550 nm. Width of wave guide>3 μm, in one embodiment of the present application the waveguide width is 4 μm, so that two transverse modes, TE, exist within the waveguide0And TE1Mode(s). The wide waveguide can effectively increase the current injection area and the heat dissipation area and improve the output light power of the laser.
Therefore, the application also provides a control method of the monolithic integrated mode-tunable chaotic laser, which is used for adjusting the laser in any embodiment of the application and comprises the following steps:
and 11, applying different bias currents to the left and right sections of active equivalent pi phase shift uniform Bragg sampling gratings, and disturbing an optical field of the equivalent pi phase shift antisymmetric Bragg sampling gratings to generate chaotic light with tunable modes.
By changing the bias current of the two-end uniform sampling grating, the frequency detuning and the mutual injection strength of the two-end uniform sampling grating and the middle antisymmetric sampling grating can be changed. For example, when the bias current of the first section of uniform sampling grating is 140-160 mA, the section of sampling grating will lase at TE with a wavelength of 1550nm0Mode and TE of 1545nm1In the mode light, the bias current of the second section of the antisymmetric sampling grating is 70-90 mA, and the section will lase at TE with the wavelength of 1550nm0And TE1In the mode of light, the bias current of the third section of uniform sampling grating is 15-25 mA and is transparent current, the transmittance of the light is increased, and the reflectivity is reduced, at the moment, the first section of uniform sampling grating irradiates TE with the wavelength of 1550nm0Mode light is injected into the second antisymmetric sampled grating, where it is mode-selected, RM1Patterns are facilitated, RM2The mode is suppressed and the optical field is disturbed, so that the generated chaotic laser is emitted from the right end face of the third section of uniform sampling grating, and the TE with the wavelength of 1545nm is excited by the first section of uniform sampling grating1The mode light can not generate disturbance to the mode light and is directly emitted from the right end face of the structure, and finally the output light of the monolithic integrated mode tunable chaotic laser chip is TE of 1550nm with the wavelength as the power being larger0Chaotic light with dominant mode.
Note that the first stage uniform grating lases a 1545nm TE1The light can directly pass through the third section of the second section without reflection and then is emitted from the right end face.
In the present application, a certain mode is mainly used, and means that the optical power of the mode is the maximum among a plurality of modes. For example with TE0Chaotic light mainly refers to TE0The mode power is more dominant, so the final output is TE0Chaotic light with dominant mode. Step 12, adjusting the bias current of the left and right active equivalent pi phase shift uniform Bragg sampling grating to make the output light from TE0Mode dominated chaotic light change to TE1Chaotic light with dominant mode, or slave TE1Mode dominated chaotic light change to TE0Chaotic light with dominant mode.
For example, by using the bias current of the embodiment described in step 11 as a reference, the bias current of the uniform sampling grating in the first and third segments can be exchanged to obtain the TE with the output light having a wavelength of 1550nm1Chaotic light with dominant mode.
Fig. 2 is a schematic diagram of mode selection.
According to the single-chip integrated mode-tunable chaotic laser chip, a laser grating part adopts a left active equivalent pi phase shift uniform Bragg sampling grating and a right active equivalent pi phase shift antisymmetric Bragg sampling grating, the three active equivalent pi phase shift antisymmetric Bragg sampling gratings are respectively provided with an independent power supply electrode, and the power ratio of the optical power injected into the middle section grating to the power of the output light of the middle section grating in free running is changed by changing the bias current of the two active equivalent pi phase shift uniform Bragg sampling gratings, so that the chaotic laser can generate chaotic laser in a single mode.
Wherein the equivalent pi-phase shift antisymmetric Bragg sampling grating generates a mixed resonant wave of a forward traveling wave of a fundamental mode and a backward traveling wave of a first-order mode, and the laser waveguide supports double transverse modes, i.e., TE0And TE1Modes, and the wavelength is exactly the same, 1550nm, forming a uniform wavelength mixed mode resonance effect. Thus, there are two independent resonant modes, one being forward TE0And TE in reverse direction1By RM1To indicate that the other is TE in the forward direction1And TE in reverse direction0By RM2To show that the two resonance modes compete with each other. The active equivalent pi phase shift uniform Bragg sampling grating at two ends is adopted to select a specific mode, and different bias currents are applied to generate light to disturb the light field of the middle section grating, so that chaotic light with tunable modes is generated.
TE under the action of equivalent pi-phase shift antisymmetric Bragg sampling grating0And TE1The modes will transform into each other and form a longitudinal resonance, which we call a mixed mode resonance. By adjusting the bias current of the two equivalent pi phase shift uniform Bragg sampling gratings, the mode of the output light can be selected, and the light excited by the left and right two-segment gratingsThe chaotic light enters the middle section equivalent pi phase shift antisymmetric Bragg sampling grating and disturbs the light field of the middle section equivalent pi phase shift antisymmetric Bragg sampling grating, so that chaotic light is generated, and finally the chaotic light with the selected mode is emitted from the right end face of the structure.
Fig. 3 is a structural schematic diagram of a monolithically integrated mode-tunable chaotic laser chip material.
Wherein 102 is a laser substrate layer which is a basic support for growing the main structure of the whole laser; 103 is a lower confinement layer, which is a low refractive index epitaxial layer for optical confinement; 104 is an active layer, which is a double heterojunction or multi-layer quantum well structure formed by intrinsic semiconductor materials and realizes the conversion from electrons to photons; 105 is an upper confinement layer, which functions as the lower confinement layer, but the material is p-type doped; 106 is a grating layer; 107 layers are waveguide layers, and the waveguide structure is manufactured on the layers by a photoetching method; 101 and 108 are metal electrodes for powering the laser; 109 is an insulating layer for applying power in a specific region; 110 are electrically isolated slots to prevent current cross talk.
The semiconductor laser of the present invention is generally made of a III-V group compound semiconductor material (e.g., GaAlAs/GaAs, InGaAs/InGaP, GaAsP/InGaP, InGaAsP/InP, InGaAsP/GaAsP, AlGaInAs, etc.), and may be made of various ternary and quaternary compound semiconductor materials such As II-VI group compound semiconductor materials, IV-VI group compound semiconductor materials, etc.
FIG. 4 is a schematic diagram of holographic exposure to produce a sampled Bragg grating.
The application also provides a method for manufacturing the monolithic integrated mode-tunable chaotic laser, which is used for manufacturing the laser in any embodiment of the application and comprises the following steps:
step 21, manufacturing a sampling pattern based on a reconstruction-equivalent chirp technology on a photoetching plate to form a mask plate;
in this step, a sampling pattern based on a reconstruction-equivalent chirp technique, i.e., the equivalent λ/4 phase shift of the sampling structure, is first designed and fabricated on a reticle (photomask).
Step 22, forming a uniform seed grating structure on the photoresist covering the wafer by using a holographic exposure technology;
and step 23, manufacturing the sampling structure on photoresist by using the mask plate, and forming an equivalent grating structure on the wafer after re-etching.
The method for writing the grating on the wafer is a conventional method for writing a sampled grating, and it should be noted that the two-step exposure sequence of steps 22 and 23 for manufacturing the grating on the wafer can be interchanged.
Precise wavelength control is a unique advantage of the reconstruction-equivalent chirp technique, based on which the laser operating wavelength can be controlled within +/-0.2 nm.
The phase shift value of each section is pi, and in the middle part of each section of structure, the phase shift structure can be realized by using a uniform Bragg sampling grating and can be equivalently realized by using a sampling Bragg sampling grating, namely: the sampling structure of the sampling grating structure has phase shift with a phase shift value of pi.
The specific structure of the equivalent pi phase shift Bragg sampling grating is as follows: one sampling period in the center of the sampled Bragg grating is changed into 1.5 times of the original length, and other sampling periods are kept unchanged, so that certain reflection peaks of the sampled Bragg grating can achieve the effect similar to that of a phase-shifted sampled grating, and the characteristic corresponding to the phase shift of the Bragg grating is equivalent phase shift.
In the present application, the intermediate-section equivalent pi-phase shift antisymmetric Bragg sampling grating generates a mixed resonant wave of a forward and backward traveling wave of a fundamental mode and a forward and backward traveling wave of a first-order mode, and the laser waveguide supports a double transverse mode, i.e., TE0And TE1Modes and wavelengths are exactly the same, creating the same wavelength mixed mode resonance effect. The ratio of the power of disturbance light to the power of output light of the middle section sampling grating is changed by respectively adjusting the bias current of the left and right sections of equivalent pi phase shift uniform Bragg sampling gratings, chaotic laser is more easily generated, and the mode of the output light of the right end face of the structure is selected, so that the mode tuning is realized. The invention also has the advantages of small integrated structure volume and low cost.
Fig. 5 is a chaotic timing diagram for mode switching.
The chaotic light disclosed by the application can be seen from a timing diagram shown in fig. 5, the time sequence is disordered, and by synthesizing a bifurcation diagram shown in fig. 7, the single-chip-integrated mode-tunable chaotic laser chip disclosed by the invention can output the mode-tunable chaotic laser.
Further, the bias current of the equivalent pi phase shift uniform Bragg sampling grating for the left and right two sections of active regions is exchanged, so that the output light is output from the TE0Mode dominated chaotic light change to TE1Chaotic light with dominant mode, or slave TE1Mode dominated chaotic light change to TE0Chaotic light with dominant mode, as shown in FIGS. 5-6
FIG. 6 shows (a) TE0And (b) TE1The power profile of an antisymmetric bragg grating upon incidence of light in a mode.
The equivalent pi-phase shift antisymmetric Bragg sampling grating is adopted when the incident light (light source) is TE0In the mode, the light is reflected as TE1Mode, like this, when the incident light is TE1In the mode, the light is reflected as TE0Mode under which TE acts0And TE1The modes will be inverted from each other and longitudinal resonance will be formed.
It should be noted that the incident light and the reflected light can be defined in the same reference plane, and fig. 6 shows the simulation result, in which the left section of the anti-symmetric bragg sampling grating is a matched cavity section added in the simulation for clearly seeing the reflected light mode. Incident TE in FIG. 6(a)0Reflective TE1Is RM in the state1Mode, (b) is RM2Mode(s).
FIG. 7 shows the output TE as the injected power varies0Pattern chaotic light bifurcation diagram.
The graph is used for describing the chaotic state of light and the variable K of the horizontal axisinjIs the power ratio of input light to output light as described above, and the vertical axis represents the distribution of the extreme values of the output power.
It is noted that any numerical value in this application, such as "is", "equal to" and "about" or "approximately equal to" is intended to be synonymous. As a technical feature of the present application, any numerical value includes an error range that is allowable in engineering practice, for example, 10%, and numerical values that are shifted from the set range to the upper and lower ranges based on the numerical values of the embodiments of the present application also belong to the range indicated by the numerical values of the present application if the technical effect stated in the technical solution of the present application can be achieved.
It is to be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The above description is only an example of the present invention, and is not intended to limit the present invention. Various modifications and alterations to this invention will become apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims (9)

1. A single chip integrated mode tunable chaotic laser is characterized in that,
the active equivalent pi phase shift uniform Bragg sampling grating comprises a left section of active equivalent pi phase shift uniform Bragg sampling grating and a right section of active equivalent pi phase shift antisymmetric Bragg sampling grating in a middle section, wherein the three sections of sampling gratings are respectively provided with an independent power supply electrode, are integrated on the same chip and share a section of optical waveguide;
the equivalent pi phase shift antisymmetric Bragg sampling grating has the structure that: the basic sampling grating is an antisymmetric sampling grating, namely, in the transverse direction of the waveguide, the upper and lower lines of uniform sampling gratings with the same sampling grating period have pi phase difference by taking a central axis as a boundary; a pi phase shift structure is also introduced into the middle part of the basic sampling grating along the length direction;
the antisymmetric Bragg sampling grating is used for realizing incident light and reflectionLight in TE0And TE1Conversion between modes;
by respectively adjusting the bias current of the left and right equivalent pi phase shift uniform Bragg sampling gratings, the power ratio of input light and output light injected into the antisymmetric Bragg sampling grating in the middle section is changed, and chaotic laser output is generated.
2. The monolithically integrated mode tunable chaotic laser of claim 1,
the equivalent pi-phase shift antisymmetric Bragg sampling grating, forward TE of transmission0TE whose mode will reflect as backward1Mode, equivalently, forward TE of transport1TE whose mode will reflect as backward0Mode(s).
3. The monolithically integrated mode tunable chaotic laser of claim 1, wherein the operating wavelength is 1550nm, the equivalent pi-phase shifted uniform bragg sampled grating length is 300 μ ι η, the equivalent pi-phase shifted antisymmetric bragg sampled grating length is 400 μ ι η, and the waveguide width is 4 μ ι η.
4. The monolithically integrated mode-tunable chaotic laser of claim 1, wherein the optical waveguide comprises SiO2A material; the substrate adopts at least one of the following materials: indium phosphide, gallium arsenide, silicon.
5. The monolithically integrated, mode-tunable chaotic laser of claim 1, wherein an inalgas multiple quantum well structure is employed.
6. The monolithically integrated mode tunable chaotic laser of claim 1, wherein the equivalent pi phase shift is achieved by changing a sampling period at a central portion of the bragg sampled grating to 1.5 times a sampling period at other portions.
7. A method for manufacturing a monolithically integrated mode tunable chaotic laser, which is used for manufacturing the laser according to any one of claims 1 to 6, and which comprises the following steps:
manufacturing a sampling pattern based on a reconstruction-equivalent chirp technology on a photoetching plate to form a mask plate;
forming a uniform seed grating structure on the photoresist covering the wafer by using a holographic exposure technology;
and manufacturing the sampling structure on photoresist by using the mask plate, and forming an equivalent grating structure on the wafer after etching.
8. A control method of a single-chip integrated mode tunable chaotic laser, which is used for adjusting the laser of any one of claims 1-6, and is characterized by comprising the following steps:
by adjusting bias current applied by the left and right sections of active equivalent pi phase shift uniform Bragg sampling gratings, input light generated by the left and right sections of active equivalent pi phase shift uniform Bragg sampling gratings disturbs an optical field of the equivalent pi phase shift antisymmetric Bragg sampling gratings to generate chaotic light with tunable modes.
9. The method as claimed in claim 8, wherein the output light is output from TE by adjusting the bias current of the left and right active equivalent pi phase shift uniform Bragg sampling gratings0Mode dominated chaotic light change to TE1Chaotic light with dominant mode, or slave TE1Mode dominated chaotic light change to TE0Chaotic light with dominant mode.
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