Integrally packaged light emitting structure

Abstract

The invention provides an integrally packaged light emitting structure, which comprises a laser chip used for generating a continuous light signal; the Sagnac ring outer cavity structure is connected with the laser chip, and is used for decomposing the continuous optical signal into a first optical signal and a second optical signal, feeding back the first optical signal to the laser chip, regulating and controlling the spectrum of the continuous optical signal, narrowing the line width, and transmitting the second optical signal to the modulator chip; and the modulator chip is connected with the Sagnac ring outer cavity structure and is used for loading a radio frequency signal to the second optical signal.

Description

Technical Field

[0001] The present disclosure relates to the field of optoelectronic technology, and in particular to an integrated packaged light emitting structure. Background Art

[0002] With the increasing demand for communication capacity, optical communication technology has been widely used due to its high speed, large capacity and long-distance transmission characteristics. External cavity lasers optimize laser output through external optical elements to achieve higher frequency stability and narrower linewidth. They can reduce laser frequency noise and improve the coherence of optical signals, thus performing well in high-precision optical communication and sensing applications. Electro-optical modulation technology is a key step in achieving optical communication. By loading the information in the electrical signal onto the optical signal, the indirect modulation method using an external modulator can maintain the normal operation of the laser and has excellent characteristics such as high speed, high signal-to-noise ratio, narrow linewidth and low chirp. It has been used in high-speed optical communication technology. However, in traditional processing technology, the laser and modulator are usually separately packaged in two devices and optically interconnected through optical fiber. Although this method can achieve optical connection, the discrete packaging leads to a larger size of the optical module and brings about a larger insertion loss. Summary of the invention

[0003] 1. Technical issues to be resolved

[0004] In view of the above problems, the present disclosure provides an integrated packaged light emitting structure to at least partially solve the problems of the current light emitting structure such as large size, high optical loss, poor stability and wide line width.

[0005] (II) Technical solution

[0006] The present disclosure provides an integrated packaged optical emission structure, comprising: a laser chip, used to generate a continuous optical signal; a Sagnac ring external cavity structure, connected to the laser chip, used to decompose the continuous optical signal into a first optical signal and a second optical signal, and feed the first optical signal back to the laser chip to regulate the spectrum of the continuous optical signal to narrow the line width, and transmit the second optical signal to a modulator chip; a modulator chip, connected to the Sagnac ring external cavity structure, used to load a radio frequency signal on the second optical signal.

[0007] According to an embodiment of the present disclosure, it also includes: a temperature control system, which is arranged under the laser chip and the Sagnac ring external cavity structure and is used to control the temperature of the laser chip and the Sagnac ring external cavity structure.

[0008] According to an embodiment of the present disclosure, the Sagnac ring external cavity structure includes: a microring resonator, which is used to resonate the continuous light signal; a Sagnac ring, coupled with the microring resonators connected in series in sequence, and is used to tune the continuous light signal passing through the microring resonator to obtain the first light signal and the second light signal, and feed the first light signal back to the laser chip, and transmit the second light signal to the modulator chip.

[0009] According to an embodiment of the present disclosure, it also includes: a hot electrode, which is arranged at the microring of the microring resonator and is used to adjust the temperature of the microring resonator and change the refractive index of the waveguide constituting the ring structure of the microring resonator.

[0010] According to an embodiment of the present disclosure, the first optical signal is injected into the laser chip by way of multi-cycle delayed feedback.

[0011] According to an embodiment of the present disclosure, the laser chip and the Sagnac ring external cavity structure are connected by lens coupling, end-face butt coupling or a spot converter.

[0012] According to an embodiment of the present disclosure, the material of the modulator chip includes indium phosphide, silicon or lithium niobate.

[0013] According to an embodiment of the present disclosure, the core layer material of the Sagnac ring outer cavity structure includes indium phosphide, silicon or lithium niobate.

[0014] According to an embodiment of the present disclosure, the laser chip is one of the following chips: a Fabry-Perot cavity chip, a distributed feedback laser chip, a distributed Bragg reflection laser chip, and a reflective semiconductor optical amplifier gain chip.

[0015] According to an embodiment of the present disclosure, the laser chip, the Sagnac ring external cavity structure and the modulator chip are quasi-monolithically integrated and packaged in a tube shell.

[0016] (III) Beneficial effects

[0017] The integrated packaged light emitting structure provided by the present disclosure includes at least the following beneficial effects:

[0018] 1. The integrated packaged light emitting structure provided by the present disclosure utilizes the multi-cycle time-delay feedback between the micro-ring resonator of the Sagnac ring external cavity structure and the Sagnac ring to realize the line width narrowing function. The laser chip can achieve the line width narrowing from MHz level to about 25Hz in the range of 10 degrees Celsius to 40 degrees Celsius, which is five orders of magnitude, thereby realizing the line width narrowing, frequency stabilization and rapid tuning of the wide spectral range of the output laser.

[0019] 2. The integrated packaged light emitting structure provided by the present disclosure has good electro-optical modulation performance.

[0020] 3. The integrated packaged optical emission structure provided by the present invention is quasi-monolithically integrated with a laser chip, a Sagnac ring external cavity structure and a modulator chip, which can achieve a compact structure, reduced optical loss and high stability, and has advantages in high-speed communication and integrated applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] For a more complete understanding of the present disclosure and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, in which:

[0022] Figure 1 A schematic diagram of an integrated packaged light emitting structure provided by an embodiment of the present disclosure is schematically shown;

[0023] Figure 2 The structure diagram of the outer cavity of the Sagnac ring using the LNOI chip provided in the embodiment of the present disclosure is schematically shown;

[0024] Figure 3 A schematic diagram of an integrated packaged light emitting structure using an InP laser chip, an LNOI Sagnac ring external cavity structure, and an LNOI electro-optical (EO) modulator chip provided by an embodiment of the present disclosure is schematically shown;

[0025] Figure 4 A diagram schematically showing the variation of output frequency noise with offset frequency with or without a Sagnac ring external cavity structure provided by an embodiment of the present disclosure;

[0026] Figure 5 The small signal electro-optical bandwidth of the modulator chip provided by the embodiment of the present disclosure is schematically shown.

[0027] Description of reference numerals:

[0028] 1-Laser chip;

[0029] 2-Sagnac ring extraluminal structure;

[0030] 3- Modulator chip;

[0031] 4-Temperature control system;

[0032] a-input waveguide;

[0033] b-output waveguide;

[0034] c-transmission waveguide;

[0035] d-waveguide directional coupler;

[0036] e-first hot electrode;

[0037] f-second hot electrode;

[0038] g-microring resonator. DETAILED DESCRIPTION

[0039] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0040] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0041] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0042] Figure 1 A schematic diagram of an integrated packaged light emitting structure provided by an embodiment of the present disclosure is schematically shown.

[0043] like Figure 1 As shown, an integrated packaged light emitting structure provided by an embodiment of the present disclosure includes: a laser chip 1, a Sagnac ring external cavity structure 2 and a modulator chip 3.

[0044] Specifically, the laser chip 1 is used to generate a continuous optical signal, thereby providing a tunable optical wave. The laser chip 1 is one of the following chips: a Fabry-Perot cavity chip, a distributed feedback laser chip, a distributed Bragg reflection laser chip, and a reflective semiconductor optical amplifier gain chip, wherein the gain chip can be, for example, a high-power indium phosphide (InP) gain chip or a high-power indium gallium arsenide phosphide (InGaAsP) gain chip.

[0045] The Sagnac ring external cavity structure 2 serves as a self-injection feedback external cavity, connected to the laser chip 1, and is used to decompose the continuous light signal into a first light signal and a second light signal, and feed the first light signal that has passed through the Sagnac ring structure back to the laser chip 1, so as to regulate the spectrum of the continuous light signal to narrow the line width of the laser, that is, to adjust the coupled light wave to obtain a narrow line width output light, and transmit the second light signal to the modulator chip 3.

[0046] In an embodiment of the present disclosure, the core layer material of the Sagnac ring outer cavity structure 2 includes indium phosphide, silicon or lithium niobate.

[0047] The laser chip 1 and the Sagnac ring external cavity structure 2 are connected through lens coupling, end-face coupling or mode spot converter.

[0048] Specifically, at the connection between the laser chip 1 and the Sagnac ring external cavity structure 2, a spot converter is used to couple the light waves provided by the laser chip 1, and is used to couple the light waves of the optical gain module to the external cavity resonance module. In the embodiment of the present disclosure, the spot converter can be a double-layer inverted cone spot converter. In addition, in addition to the spot converter provided in the embodiment of the present disclosure, the light wave coupling method can also be lens coupling, photon lead stitching, etc., and relevant technicians can choose according to actual conditions, and the embodiment of the present disclosure is not limited here.

[0049] The modulator chip 3 is connected to the Sagnac ring external cavity structure 2 and is used to load a radio frequency signal onto the second optical signal.

[0050] In the embodiment of the present disclosure, the material used by the modulator chip 3 includes indium phosphide (InP) or silicon or thin film lithium niobate (LNOI), and the Sagnac ring external cavity structure 2 and the modulator chip 3 use the same material to achieve monolithic integration.

[0051] It can be understood that the optical emission module based on the Sagnac ring external cavity structure provided in the embodiment of the present disclosure can effectively narrow the output line width of the laser chip, and is monolithically integrated and packaged with the modulator chip to form an efficient optical emission structure, which has the characteristics of convenient design, compact structure and integrated miniaturization.

[0052] Continue to refer to Figure 1 The light emitting structure also includes: a temperature control system 4, which is arranged under the laser chip 1 and the Sagnac ring external cavity structure 2 and is used to control the temperature of the laser chip 1 and the Sagnac ring external cavity structure 2.

[0053] On the basis of the above embodiments, in this embodiment, the temperature control system 4 includes at least a high-precision temperature sensor and a temperature control element (such as a thermocouple, a thermistor or a semiconductor refrigerator, etc.), which can monitor and accurately adjust the operating temperature of the laser chip 1 and the Sagnac ring external cavity structure 2 in real time, thereby effectively suppressing the optical characteristic drift and performance degradation caused by temperature changes.

[0054] In an embodiment of the present disclosure, a Sagnac ring external cavity structure includes: a microring resonator for resonating a continuous optical signal; a Sagnac ring coupled to the microring resonators connected in series, for tuning the continuous optical signal passing through the microring resonator to obtain a first optical signal and a second optical signal, and feeding the first optical signal back to the laser chip, and transmitting the second optical signal to the modulator chip.

[0055] Optionally, the microring resonator can be composed of a silicon on insulating substrate (SOI) waveguide microring resonator or a high quality factor thin film lithium niobate (LNOI) waveguide microring resonator or an indium phosphide (InP) waveguide microring resonator. The Sagnac ring external cavity structure is composed of at least one traditional microring resonator and one Sagnac ring. The number of microring resonators can be one or more.

[0056] It should be noted that the light splitting of the couplers between the Sagnac rings and between the Sagnac rings and the microring resonator can be arbitrary, and the coupling ratio can be fixed or the coupling ratio can be adjustable.

[0057] As an optional implementation scheme, the Sagnac ring outer cavity structure 2 adopts a LNOI chip.

[0058] Figure 2 The structure diagram of the outer cavity of a Sagnac ring using an LNOI chip provided in an embodiment of the present disclosure is schematically shown.

[0059] like Figure 2 As shown, the Sagnac ring external cavity structure 2 includes an input waveguide a, an output waveguide b, a transmission waveguide c, a waveguide directional coupler d, a first heating electrode e, a second heating electrode f and a microring resonator g. Among them, the input waveguide a is used to input laser (i.e., continuous light signal), the transmission waveguide c, the waveguide directional coupler d, and the microring resonator g act together to control the spectrum of the laser to narrow the line width, the waveguide coupler adopts an adjustable ratio, and the output waveguide b is used to output the laser after the line width is narrowed.

[0060] Furthermore, it also includes: a hot electrode, which is arranged at the microring of the microring resonator and is used to adjust the temperature of the microring resonator and change the refractive index of the waveguide constituting the ring structure of the microring resonator.

[0061] Continue to refer to Figure 2A first thermode e can be placed at the transmission waveguide c of the Sagnac ring to adjust the position of the resonant wavelength during self-injection feedback, and a second thermode f can be placed at the microring of the microring resonator g. The temperature of the microring resonator g can be adjusted by using the thermode, and the refractive index of the waveguide can be changed by controlling the current of the thermode f.

[0062] It can be understood that the first optical signal is injected into the laser chip by means of multi-cycle delayed feedback. Using the principle of multi-cycle delayed feedback, different delay cavity lengths constitute multiple cycles. After passing through the Sagnac ring, the laser will return in multiple different cycles. Therefore, feedback of multiple wavelengths of light can be achieved, realizing wavelength tuning locking and linewidth narrowing in a wide spectral range.

[0063] In the embodiment of the present disclosure, the laser chip 1, the Sagnac ring external cavity structure 2 and the modulator chip 3 are quasi-monolithically integrated and packaged in a tube shell, thereby forming a highly integrated, high-performance optical transmission module.

[0064] The integrated packaged light emitting structure provided by the present disclosure may be packaged in a variety of ways, such as TO packaging, butterfly packaging or BGA packaging.

[0065] Embodiment 1:

[0066] Figure 3 The schematic diagram of the light emitting structure provided by the embodiment of the present disclosure using an InP laser chip, an LNOI Sagnac ring external cavity structure, and an LNOI electro-optical (EO) modulator chip in an integrated package is schematically shown.

[0067] like Figure 3As shown, in the disclosed embodiment, a distributed feedback (DFB) cavity is selected as the laser chip, InP material is selected, and current is injected into the phase region structure of the laser chip by an external steady current source. A mode spot converter is selected to couple the light on the laser chip to the feedback external cavity structure. The Sagnac ring and microring resonator in the Sagnac ring external cavity structure are prepared by waveguides made of thin-film lithium niobate (LNOI) material, using x-cut thin-film lithium niobate, the waveguide loss is 0.2dB / cm, the thickness of the thin-film lithium niobate layer is 400 nm, the waveguide width is 1μm, the thermo-optical effect is used to change the waveguide phase, and heating electrodes are placed on the Sagnac ring and microring resonator. A waveguide directional coupler with a fixed coupling coefficient is selected, wherein the coupling interval is 200nm and the coupling length is 3μm. After undergoing multi-cycle delayed feedback, a narrowed laser input electro-optic modulator chip is obtained. The electro-optic modulator chip is also made of thin-film lithium niobate (LNOI) material. LNOI has a high electro-optic coefficient and a half-wave voltage of 2V. Integrate InP laser chip and LNOI Sagnac ring external cavity structure and LNOI electro-optic (EO) modulator chip. The light emission structure based on LiNbO3 photonic integrated circuit can realize ultra-narrow linewidth laser. By packaging, III-V lasers are combined with LNOI on a non-uniform integration platform, and LNOI chip is heterogeneously integrated with InP-based DFB laser, and the output light can achieve linewidth narrowing, wide tuning and frequency stability.

[0068] The implementation process of realizing ultra-narrow linewidth laser based on the light emission structure of LiNbO3 photonic integrated circuit is as follows: the DFB laser outputs laser, the spot converter couples the light on the laser chip to the Sagnac ring external cavity structure, and the laser enters the Sagnac ring and multiple microring resonators. Due to the different lengths of the microrings, the laser will return to the laser chip in multiple different cycles after passing through the Sagnac ring, and injection locking is achieved at multiple cycles and time points, which effectively increases the equivalent cavity length of the laser and the lifetime of the photons in the cavity. Finally, the linewidth of the laser micro-output light output from the other end of the Sagnac ring is narrowed, and finally enters the modulator chip for electro-optical modulation, forming an integrated packaged light emission structure as a whole.

[0069] Figure 4 The diagram schematically shows the variation of the output frequency noise with the offset frequency with and without the Sagnac ring external cavity structure provided by the embodiment of the present disclosure.

[0070] like Figure 4As shown in the figure, the change of output frequency noise with offset frequency can characterize the output linewidth performance of the laser. By comparing the output frequency with offset frequency noise curves with and without Sagnac ring external cavity structure, it can be seen that when the ambient temperature is room temperature, the intrinsic linewidth of the DFB laser is about 1.25 MHz, while the linewidth of the laser based on the LNOI external cavity can reach 26 Hz. Compared with the original laser intrinsic linewidth, the linewidth of the LNOI external cavity laser is narrowed by 5 orders of magnitude.

[0071] Figure 5 The small signal electro-optical bandwidth of the modulator chip provided by the embodiment of the present disclosure is schematically shown.

[0072] like Figure 5 As shown, the 3dB bandwidth on the S21 curve characterizes the signal transmission capability of the modulator chip. It can be seen from the S21 curve that the small signal electro-optical bandwidth of the modulator exceeds 50 GHz.

[0073] In the related art, it is of great significance to integrate the laser and the modulator into an optical transmission module. Integrated optoelectronic technology can realize the miniaturization and energy saving of optical communication equipment. It is not only an important development direction in the field of optical communication, but also widely used in popular research directions such as laser radar and phased array radar. The integrated packaged optical transmission structure provided by the embodiment of the present disclosure has the advantages of low noise, high side mode suppression ratio, high temperature stability, narrow linewidth, high electro-optical bandwidth, miniaturization and integration. By quasi-monolithically integrating the laser chip with the Sagnac ring external cavity structure and the modulator chip, good high-speed performance is achieved while narrowing the linewidth, so that it has both the high reliability and low power consumption characteristics of a monolithic integrated structure.

[0074] It will be appreciated by those skilled in the art that the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways, even if such combinations and / or combinations are not explicitly described in the present disclosure. In particular, the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways without departing from the spirit and teachings of the present disclosure. All of these combinations and / or combinations fall within the scope of the present disclosure.

[0075] Although the present disclosure has been shown and described with reference to specific exemplary embodiments of the present disclosure, it should be understood by those skilled in the art that various changes in form and details may be made to the present disclosure without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents. Therefore, the scope of the present disclosure should not be limited to the above-mentioned embodiments, but should be determined not only by the appended claims, but also by the equivalents of the appended claims.

Claims

1. An integrated packaged light emitting structure, characterized in that: include: A laser chip for generating a continuous optical signal; A Sagnac ring external cavity structure, connected to the laser chip, for decomposing the continuous optical signal into a first optical signal and a second optical signal, feeding the first optical signal back to the laser chip to regulate the spectrum of the continuous optical signal to narrow the line width, and transmitting the second optical signal to a modulator chip; A modulator chip is connected to the Sagnac ring external cavity structure and is used to load a radio frequency signal onto the second optical signal.

2. The integrated packaged light emitting structure according to claim 1, characterized in that: Also includes: The temperature control system is arranged under the laser chip and the Sagnac ring external cavity structure, and is used to control the temperature of the laser chip and the Sagnac ring external cavity structure.

3. The integrated packaged light emitting structure according to claim 1, characterized in that: The Sagnac ring outer cavity structure comprises: A microring resonator, used to resonate the continuous optical signal; The Sagnac ring is coupled to the microring resonators connected in series, and is used to tune the continuous optical signal passing through the microring resonator to obtain the first optical signal and the second optical signal, and feed the first optical signal back to the laser chip, and transmit the second optical signal to the modulator chip.

4. The integrated packaged light emitting structure according to claim 3, characterized in that: Also includes: The hot electrode is arranged at the microring of the microring resonator and is used to adjust the temperature of the microring resonator and change the refractive index of the waveguide constituting the annular structure of the microring resonator.

5. The integrated packaged light emitting structure according to claim 1 or 3, characterized in that: The first optical signal is injected into the laser chip by means of multi-cycle delayed feedback.

6. The integrated packaged light emitting structure according to claim 1, characterized in that: The laser chip and the Sagnac ring external cavity structure are connected through lens coupling, end-face butt coupling or a spot converter.

7. The integrated packaged light emitting structure according to claim 1, characterized in that: The material of the modulator chip includes indium phosphide, silicon or lithium niobate.

8. The integrated packaged light emitting structure according to claim 1, characterized in that: The core layer material of the Sagnac ring outer cavity structure includes indium phosphide, silicon or lithium niobate.

9. The integrated packaged light emitting structure according to claim 1, characterized in that: The laser chip is one of the following chips: a Fabry-Perot cavity chip, a distributed feedback laser chip, a distributed Bragg reflection laser chip and a reflective semiconductor optical amplifier gain chip.

10. The integrated packaged light emitting structure according to claim 1, characterized in that: The laser chip, the Sagnac ring external cavity structure and the modulator chip are quasi-monolithically integrated and packaged in a tube shell.

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