A direct modulation multi-section distributed feedback semiconductor laser

Abstract

The application discloses a direct modulation multi-section distributed feedback semiconductor laser, which comprises a high reflection film, an active phase shift region, a distributed feedback lasing region, an active grating reflection region and an anti-reflection film, and the active phase shift region, the distributed feedback lasing region and the active grating reflection region have the same epitaxial structure and waveguide structure parameters. By adopting the technical scheme, the active phase shift region is arranged between the high reflection film and the distributed feedback lasing region, the distributed feedback lasing region and the active grating reflection region have the same epitaxial structure and waveguide structure parameters, carrier fluctuation caused by phase uncertainty of the high reflection film end face can be buffered, the laser has more consistent output, grating residual phase is avoided during dissociation, and therefore, the yield of the laser is improved; the same epitaxial structure and waveguide parameters are used, and different currents are injected to manufacture grating center wavelength detuning, complex epitaxial technology is avoided, the manufacturing difficulty is reduced, and the cost is lowered.

Description

Technical Field

[0001] This invention relates to the field of optoelectronics technology, and in particular to a direct-modulated multi-segment distributed feedback semiconductor laser. Background Technology

[0002] Semiconductor lasers are a key focus in the development of high-speed optical communication networks. As the light source in optical communication systems, they require high modulation rates and stable output characteristics. Currently, two commonly used modulation schemes are direct modulation and external modulation. Direct modulation involves applying a modulation current to the injection current of the semiconductor laser, allowing the laser to directly output the modulated optical signal. External modulation involves fabricating or connecting a separate modulator outside the complete semiconductor laser. In this case, a stable DC current is injected into the semiconductor laser to maintain the optical output, while the external modulator performs the modulation. Compared to external modulation schemes, direct-modulated lasers (DMLs) offer advantages such as low cost, small size, and simple fabrication, and are therefore widely used in optical communication. Among them, distributed feedback (DFB) lasers with Bragg grating structures are particularly favored due to their excellent single-mode output characteristics and simple manufacturing process.

[0003] Using multiple quantum wells as the active layer allows distributed feedback (DFB) semiconductor lasers to achieve both low threshold and high slope efficiency while maintaining a shorter cavity length, thereby increasing the modulation bandwidth of direct modulation. However, due to the relaxation oscillation effect, the modulation bandwidth and output chirp characteristics of directly modulated lasers are worse than those of externally modulated lasers, thus limiting their use in long-distance high-speed communication systems. In addition, the phase uncertainty of high-reflectivity thin films and the randomness of end-face grating truncation result in a low yield of distributed feedback (DFB) semiconductor lasers.

[0004] To improve the bandwidth of directly modulated lasers, numerous solutions have been proposed, among which detuning loading and photon-photon resonance effects are widely used. However, both of these effects require the addition of a feedback region outside the injected active region, as well as precise control of the detuning amount. Using a passive or different active layer feedback region greatly increases the difficulty and cost of epitaxial fabrication, and due to process errors, it is difficult to control the detuning amount using methods such as grating periodization or fixed phase shift regions. Summary of the Invention

[0005] The uncertainty in the reflection phase at the feedback region end face stems from two main factors. First, the manufacturing process of the high-reflectivity film limits the thickness and composition of the reflective film under the same manufacturing process, resulting in a random distribution of the reflection phase between 0 and 2π. Second, during end face dissociation, the uncontrollable residue of the grating adds a random phase to the reflection. This phase uncertainty leads to significant differences in the output spectra of distributed feedback (DFB) lasers with the same structural parameters, thus reducing the yield of lasers in the same batch.

[0006] In view of the technical problem of uncertainty in the reflection phase at the end face of the feedback region, the present invention provides an active phase shift region between the high-reflection film and the distributed feedback lasing region, and proposes an embodiment of the present invention to provide a direct-modulated multi-segment distributed feedback semiconductor laser that overcomes or at least partially solves the above problems.

[0007] This invention discloses a direct-modulated multi-segment distributed feedback semiconductor laser. The semiconductor laser includes a high-reflection film, an active phase-shift region, a distributed feedback lasing region, an active grating reflection region, and an anti-reflection film arranged sequentially. The active phase-shift region, the distributed feedback lasing region, and the active grating reflection region have the same epitaxial structure and waveguide structure parameters.

[0008] A first independent electrode is provided on the active phase shift region, and the first independent electrode is used to input a first current signal to the active phase shift region;

[0009] The distributed feedback lasing region is provided with a second independent electrode and a grating phase shift module. The second independent electrode is used to input a second current signal into the distributed feedback lasing region. The second current signal includes a bias current and a modulation current signal. The grating phase shift module is used to provide a fixed phase shift amount.

[0010] A third independent electrode is provided on the active grating reflective area, and the third independent electrode is used to input a third current signal to the active grating reflective area.

[0011] Optionally, the distributed feedback lasing region and the active grating reflection region use the same active layer and the same grating period. By injecting different second current signals and the third current signals, the equivalent refractive index is adjusted, so that the grating Bragg wavelength of the distributed feedback lasing region and the active grating reflection region produces a detuning effect.

[0012] Optionally, the grating coupling coefficient between the distributed feedback lasing region and the active grating reflection region is no greater than 50 cm. -1 The center wavelength of the Bragg grating has a detuning of no more than 1 nanometer.

[0013] Optionally, the high-reflectivity film is located at one end face of the active phase-shift region, and the reflectivity of the high-reflectivity film is greater than 95%.

[0014] Optionally, the anti-reflective film is located on one end face of the active grating reflective region, and the reflectivity of the anti-reflective film is less than 1%.

[0015] Optionally, the length of the active phase-shifting region is not less than 10 micrometers, and there is no etched grating on the active phase-shifting region, which is used to buffer the carrier fluctuations caused by the uncertainty of the reflection phase of the high-reflection film, and to control the overall round-trip phase of the laser through the first current signal generated by the first independent electrode.

[0016] Optionally, the length of the distributed feedback lasing region is no more than 300 micrometers, and the grating phase shift module is located in the middle of the distributed feedback lasing region.

[0017] Optionally, the phase shift of the grating phase shift module is 0.3π.

[0018] Optionally, the length of the active grating reflective region is no greater than 500 micrometers.

[0019] This invention discloses a directly modulated multi-segment distributed feedback semiconductor laser. The semiconductor laser includes a high-reflection film, an active phase-shift region, a distributed feedback lasing region, an active grating reflection region, and an anti-reflection film, all sequentially distributed. The active phase-shift region, the distributed feedback lasing region, and the active grating reflection region have the same epitaxial structure and waveguide structure parameters. By employing the above technical solution, this invention has the following technical effects:

[0020] (1) An active phase shift region is set between the high reflectivity film and the distributed feedback lasing region. The distributed feedback lasing region and the active grating reflection region have the same epitaxial structure and waveguide structure parameters, which can buffer the carrier fluctuation caused by the phase uncertainty of the high reflectivity film end face, so that the laser has a more consistent output and avoids the generation of grating residual phase during dissociation, thereby improving the laser yield.

[0021] (2) Using the same epitaxial structure and waveguide parameters, different currents are injected to create grating center wavelength detuning, which avoids complex epitaxial processes, reduces manufacturing difficulty, and lowers costs.

[0022] (3) An independent electrode is set up above the active phase shift region. The equivalent refractive index of the region is controlled by microcurrent to control the overall optical field phase of the laser. Combined with the detuning loading and PPR effect, the bandwidth of the direct-modulated laser can be effectively improved. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a directly modulated multi-segment distributed feedback semiconductor laser provided in an embodiment of the present invention;

[0024] Figure 2 A schematic diagram of the round-trip gain and round-trip phase of a directly modulated multi-segment distributed feedback semiconductor laser when different currents are injected into the active phase shift region, as provided in an embodiment of the present invention.

[0025] Figure 3A schematic diagram of the round-trip gain and round-trip phase of a directly modulated multi-segment distributed feedback semiconductor laser under example parameters provided by the present invention;

[0026] Figure 4 The laser lasing spectrum of a directly modulated multi-segment distributed feedback semiconductor laser provided by the present invention under example parameters.

[0027] Figure 5 A curve showing the small-signal response of a directly modulated multi-segment distributed feedback semiconductor laser provided by the present invention;

[0028] Figure 1 In the diagram, 1. Distributed feedback lasing region, 2. Active grating reflection region, 3. Active phase shift region, 4. High reflectivity film, 5. Antireflection film, 11. Second independent electrode, 12. Grating phase shift module, 21. Third independent electrode, 31. First independent electrode. Detailed Implementation

[0029] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0030] Figure 1 This is a schematic diagram of a directly modulated multi-segment distributed feedback semiconductor laser provided in an embodiment of the present invention. The semiconductor laser includes a distributed feedback lasing region 1, an active grating reflection region 2, an active phase shift region 3, a high-reflectivity film 4, and an anti-reflection film 5. The distributed feedback lasing region 1, the active grating reflection region 2, and the active phase shift region 3 have the same epitaxial structure and waveguide structure parameters, resulting in a more consistent output from the semiconductor laser. The high-reflectivity film 4 is located on one end face of the active phase shift region 3. The high-reflectivity film 4 has a reflectivity greater than 95%, used to provide sufficient optical feedback to the laser and reduce the overall threshold voltage of the laser. The anti-reflection film 5 is located on one end face of the active grating reflection region 2. The anti-reflection film 5 has a reflectivity less than 1%, used to reduce the impact of reflected light on the laser and to maximize the output power of the exit surface.

[0031] A second independent electrode 11 and a grating phase-shifting module 12 are disposed on the distributed feedback lasing region 1. The second independent electrode 11 is used to input a second current signal into the distributed feedback lasing region. This second current signal includes a bias current and a modulation current signal I1, thereby realizing direct modulation of the DFB laser. The grating phase-shifting module 12 is located in the middle of the distributed feedback lasing region 1 and is used to provide a fixed phase shift. For example, the phase shift of the grating phase-shifting module can be 0.3π, which introduces a fixed phase shift so that the dominant mode and the PPR mode are located near the center wavelength. It should be noted that those skilled in the art can set the phase shift of the grating phase-shifting module according to actual needs. The embodiment of this application does not limit the value of the fixed phase shift.

[0032] A third independent electrode 21 is disposed on the active grating reflector region 2. The third independent electrode 21 is used to input a third current signal I2 into the active grating reflector region. This third current signal I2 serves two purposes: firstly, it ensures a certain carrier concentration, reducing light loss; secondly, it alters the equivalent refractive index, resulting in a detuning of less than 1 nanometer between the Bragg wavelength of the grating and the Bragg wavelength of the distributed feedback lasing region 1, thus satisfying the detuning loading and photon-photon resonance (PPR) effect. By using the same epitaxial structure and waveguide parameters, and injecting different currents to create grating center wavelength detuning, complex epitaxial processes can be avoided, fabrication difficulty reduced, and the manufacturing cost of semiconductor lasers lowered.

[0033] An independent first electrode 31 is provided on the active phase shift region 3. The first independent electrode 31 is used to input a first current signal I3 to the active phase shift region 3. In this embodiment, the value of the first current signal I3 is no greater than 15mA. In actual use, sufficient electrical isolation is required between the first independent electrode 31, the second independent electrode 21, and the third independent electrode 11 to avoid mutual interference.

[0034] Using the above technical solution, the embodiments of the present invention can improve the modulation bandwidth of a directly modulated laser through detuning loading and photon-photon resonance (PPR) effect. This requires a certain amount of detuning between the gratings of the distributed feedback lasing region 1 and the active grating reflection region 2. The present invention uses the change in equivalent refractive index caused by different injection currents to control this detuning, avoiding complex processes in the grating period or grating structure, thus reducing the manufacturing difficulty and cost. It should be noted that in the embodiments, the length of the distributed feedback lasing region 1 is no greater than 300 micrometers, the length of the active grating reflection region 2 is no greater than 500 micrometers, and the coupling strength between the two grating parts is no greater than 50 cm⁻¹. The length of the active phase shift region 3 is no less than 10 micrometers. The phase shift in the grating of the distributed feedback (DFB) lasing region is located at the center of the region, and the phase shift is 0.3π, which serves to introduce a fixed phase shift, so that the main mode and the PPR mode are located near the center wavelength.

[0035] To improve the yield of the laser, this invention introduces an active phase-shifting region 3 between the distributed feedback lasing region 1 and the end face of the high-reflectivity film 4. This region can prevent grating residue from being generated during end face dissociation and can also buffer carrier concentration fluctuations caused by the uncertainty of the reflection phase of the high-reflectivity film 5, thereby increasing the yield of the laser. In addition, this invention adds an independent electrode 31 above the active phase-shifting region 3, which can inject a micro-current not exceeding a threshold value to control the equivalent refractive index change of the active phase-shifting region 3, making the round-trip phase of the overall optical field of the laser controllable and generating detuned loading and photon-photon resonance (PPR) effects more efficiently.

[0036] Figure 2 This is a schematic diagram of the round-trip gain and round-trip phase of a directly modulated multi-segment distributed feedback semiconductor laser when different currents are injected into the active phase shift region, as provided in an embodiment of the present invention. When the injection current I3 in the active phase shift region 3 changes, the round-trip phase spectrum of the laser will shift vertically as a whole, indicating that the active phase shift region 3 can control the overall round-trip phase of the laser. This is beneficial for artificially selecting the lasing wavelength and detuning amount within a certain range, making the detuning loading effect and PPR effect more controllable and efficient.

[0037] Figure 3 This invention provides a schematic diagram of the round-trip gain and round-trip phase of a directly modulated multi-segment distributed feedback semiconductor laser under example parameters. When the phase is an integer multiple of 2π and the gain is greater than 1, the lasing master mode can be selected. Due to the detuning of the grating center wavelength between the distributed feedback (DFB) lasing region 1 and the active grating feedback region 2, the lasing master mode of the laser is located at the falling edge of the round-trip gain spectrum, thus satisfying the detuning loading effect condition, which can increase the relaxation oscillation frequency of the laser, thereby increasing the modulation bandwidth of the laser. In addition, there is a potential PPR mode at a distance of 0.22 nm in the long wavelength direction. When the modulation frequency approaches 42 GHz, the PPR mode will be enhanced, and a PPR frequency response peak will appear, further increasing the modulation bandwidth.

[0038] Figure 4 The laser lasing spectrum of a directly modulated multi-segment distributed feedback semiconductor laser provided by this invention is shown under example parameters. The bias current I1 in the distributed feedback (DFB) lasing region 1 is 100mA, the current I2 in the active grating feedback region 2 is 15mA, and the injection current I3 in the active waveguide region 3 is 2mA. Figure (a) shows the laser lasing spectrum without a modulation signal, where a potential PPR peak can be seen on the long wavelength side of the dominant mode. Figure (b) shows the laser lasing spectrum with a 42GHz modulation signal, where the modulation signal enhances the PPR peak, increasing its frequency response.

[0039] Figure 5The small-signal response curve of a directly modulated multi-segment distributed feedback semiconductor laser provided by this invention shows that when the bias current I1 of the distributed feedback (DFB) lasing region 1 is 60mA and the current I2 of the active grating feedback region 2 is 0mA, the detuning loading effect and PPR effect are not obvious, the relaxation oscillation frequency is low, and the bandwidth is 30GHz. When the bias current I1 of the distributed feedback (DFB) lasing region 1 is 100mA and the current I2 of the active grating feedback region 2 increases from 0mA to 15mA, the overall 3dB bandwidth of the laser increases from 47GHz to 52GHz, and the relaxation oscillation peak shifts to the position of 20GHz. There is also a significant PPR peak around 42GHz, indicating that the structure successfully satisfies the detuning loading and PPR effects to improve the modulation bandwidth of the laser.

[0040] This invention discloses a directly modulated multi-segment distributed feedback semiconductor laser. The semiconductor laser includes a high-reflection film, an active phase-shift region, a distributed feedback lasing region, an active grating reflection region, and an anti-reflection film, all sequentially distributed. The active phase-shift region, the distributed feedback lasing region, and the active grating reflection region have the same epitaxial structure and waveguide structure parameters. By employing the above technical solution, this invention has the following technical effects:

[0041] (1) An active phase shift region is set between the high reflectivity film and the distributed feedback lasing region. The distributed feedback lasing region and the active grating reflection region have the same epitaxial structure and waveguide structure parameters, which can buffer the carrier fluctuation caused by the phase uncertainty of the high reflectivity film end face, so that the laser has a more consistent output and avoids the generation of grating residual phase during dissociation, thereby improving the laser yield.

[0042] (2) Using the same epitaxial structure and waveguide parameters, different currents are injected to create grating center wavelength detuning, which avoids complex epitaxial processes, reduces manufacturing difficulty, and lowers costs.

[0043] (3) An independent electrode is set up above the active phase shift region. The equivalent refractive index of the region is controlled by microcurrent to control the overall optical field phase of the laser. Combined with the detuning loading and PPR effect, the bandwidth of the direct-modulated laser can be effectively improved.

[0044] It should be noted that, for the sake of simplicity, the above embodiments are all described as a series of actions. However, those skilled in the art should understand that the embodiments of the present invention are not limited to the described order of actions, because according to the embodiments of the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily essential to the embodiments of the present invention.

[0045] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0046] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, apparatus, or computer program products. Therefore, embodiments of the present invention can take the form of entirely hardware embodiments, entirely software embodiments, or embodiments combining software and hardware aspects. Furthermore, embodiments of the present invention can take the form of computer program products implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0047] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0048] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0049] The above provides a detailed description of a direct-modulated multi-segment distributed feedback semiconductor laser provided by the present invention. Specific examples have been used to illustrate the principle and implementation of the present invention. For those skilled in the art, based on the idea of ​​the present invention, there will be changes in the specific implementation and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A directly modulated multi-segment distributed feedback semiconductor laser, characterized in that, The semiconductor laser comprises a high-reflection film, an active phase-shift region, a distributed feedback lasing region, an active grating reflection region, and an anti-reflection film arranged sequentially, and the active phase-shift region, the distributed feedback lasing region, and the active grating reflection region have the same epitaxial structure and waveguide structure parameters. A first independent electrode is provided on the active phase shift region, and the first independent electrode is used to input a first current signal to the active phase shift region; The distributed feedback lasing region is provided with a second independent electrode and a grating phase shift module. The second independent electrode is used to input a second current signal into the distributed feedback lasing region. The second current signal includes a bias current and a modulation current signal. The length of the distributed feedback lasing region is no greater than 300 micrometers, and the grating phase shift module is located in the middle of the distributed feedback lasing region. The grating phase shift module is used to provide a fixed phase shift amount. A third independent electrode is provided on the active grating reflective region, and the third independent electrode is used to input a third current signal to the active grating reflective region; The length of the active phase shift region is not less than 10 micrometers. There is no etched grating on the active phase shift region. It is used to buffer the carrier fluctuations caused by the uncertainty of the reflection phase of the high-reflection film, and to control the overall round-trip phase of the semiconductor laser through the first current signal. The high-reflectivity film is located at one end face of the active phase-shift region, and the reflectivity of the high-reflectivity film is greater than 95%. The distributed feedback lasing region and the active grating reflection region use the same active layer and the same grating period. By injecting different second current signals and the third current signals, the equivalent refractive index is adjusted, causing the grating Bragg wavelength of the distributed feedback lasing region and the active grating reflection region to produce a detuning effect.

2. The semiconductor laser according to claim 1, characterized in that, The grating coupling coefficient between the distributed feedback lasing region and the active grating reflection region is no greater than 50 cm. -1 The center wavelength of the Bragg grating has a detuning of no more than 1 nanometer.

3. The semiconductor laser according to claim 1, characterized in that, The anti-reflection film is located on one end face of the active grating reflective area, and the reflectivity of the anti-reflection film is less than 1%.

4. The semiconductor laser according to claim 1, characterized in that, The phase shift of the grating phase shift module is 0.3π.

5. The semiconductor laser according to claim 1, characterized in that, The length of the active grating reflective region is no greater than 500 micrometers.

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