DFB Laser Array Research Articles

ICP刻蚀优化及在多波长分布反馈式激光器阵列中的应用

ICP刻蚀优化及在多波长分布反馈式激光器阵列中的应用

EML Array fabricated by SAG technique monolithically integrated with a buried ridge AWG multiplexer

We report the fabrication of a ten channel electroabsorption modulated DFB laser (EML) array. Different emission wavelengths of the laser array are obtained by selective area growth (SAG) technique, which is also used for the integration of electroabsorption modulators (EAM) with the lasers. An arrayed waveguide grating (AWG) combiner is integrated monolithically with the laser array by butt-joint regrowth (BJR) technique. A buried ridge waveguide structure is adopted for the AWG combiner. A self aligned fabrication procedure is adopted for the fabrication of the waveguide structure of the device to eliminate the misalignment between the laser active waveguide and the passive waveguide. A Ti thin film heater is integrated for each laser in the array. With the help of the heaters, ten laser emissions with 1.8nm channel spacing are obtained. The integrated EAM has a larger than 11dB static extinction ratios and larger than 8GHz small signal modulation bandwidths. The light power collected in the output waveguide of the AWG is larger than −13dBm for each wavelength.

30-km Error-Free Transmission of Directly Modulated DFB Laser Array Transmitter Optical Sub-Assembly for 100-Gb Application

We fabricated the first compact 100-gigabit Ethernet (100GbE) transmitter optical sub-assembly (TOSA) using a directly modulated DFB laser (DML) array monolithically integrated with an optical multiplexer. Specially designed InGaAlAs/InGaAlAs multiple quantum wells make it possible to obtain a large gain in the 1295–1310-nm wavelength range and to operate at a high temperature of 55 °C. The four-channel DML array chip is only $2.0 \,\text{mm} \times 2.4 \,\text{mm}$ in size, and the fabricated TOSA is only $7.2 \,\text{mm} (W) \times 14.3 \,\text{mm} (L) \times 6.5 \,\text{mm} (H)$ , which fits a CFP2 or smaller 100-GbE transceiver. For all the lanes, the 3-dB bandwidths of the TOSA exceeded 17 GHz, and it could operate at 25.8 Gb/s. With 25.8-Gb/s × four-channel simultaneous operation, error-free transmissions over a 30-km single-mode fiber were demonstrated for all the lanes.

Low-crosstalk operation of directly modulated DFB laser array TOSA for 112-Gbit/s application.

A directly modulated DFB laser (DML) array transmitter optical sub-assembly (TOSA) operating at 112 Gbit/s was fabricated for the first time. The DML array chip, which was integrated with a GND pad, and the DML array sub-assembly were designed to suppress the adjacent electrical crosstalk of the DML array TOSA. The 3-dB bandwidths of the fabricated TOSA exceeded 18 GHz. The electrical crosstalk of the TOSA was suppressed to less than -20 dB below 18GHz. Under simultaneous 4-channel 28-Gbit/s (112 Gbit/s) operation, the OTU4 mask margins were degraded by a maximum of only 6% compared with those under discrete operation. Error-free transmissions over a 10-km single-mode fiber were demonstrated for all the lanes under 112-Gbit/s operation.

Monolithically integrated 4 ch × 25.8 Gbps lens-integrated surface-emitting DFB laser array directly coupled to SMF

Monolithically integrated 4 ch × 25.8 Gbps lens-integrated surface-emitting DFB laser array directly coupled to SMF

A Multi-Channel Etched-Mesa PBH DFB Laser Array Using an SAG Technique

We present a multi-channel $\lambda $ /4-shifted distributed feedback laser diode array (DFB-LDA) for the low-cost application of wavelength division multiplexing-based datacenter networks. The gain spectrum and lasing wavelength of each channel are controlled by utilizing selective area growth and E-beam lithography techniques, respectively. To reduce the power consumption and improve the channel uniformity of the proposed array, a planar-buried hetero-structure (PBH) is introduced and the region containing the active region and the current blocking structures are etched in a mesa form (i.e., an etched mesa PBH). From this study, it was found that an 8-channel 300- $\mu \text{m}$ -long anti-reflection (AR) $\lambda $ /4-shifted DFB-LDA has a threshold current of 10 mA, ±1.5 mA, and a side mode suppression ratio of over 50 dB for all channels. A transmission test for this LDA showed a clear eye opening with a dynamic ratio of over 4.5 dB at 10 Gb/s, and a power penalty of less than 2 dB after a 2-km transmission.

Study on Two-Section DFB Lasers and Laser Arrays Based on the Reconstruction Equivalent Chirp Technique and Their Application in Radio-Over-Fiber Systems

Two-section distributed feedback (TS-DFB) semiconductor lasers based on the reconstruction equivalent chirp technique is proposed. A four-channel TS-DFB laser array (TS-DFB-LA) is theoretically studied and experimentally demonstrated. Compared with the conventional one-section DFB lasers, the proposed TS-DFB lasers have much higher output efficiency and higher side-mode suppression ratio (SMSR) when both the facets of the laser cavity are coated with antireflection coatings. About 39% increase in output efficiency, more than 10 mA decrease in threshold current, and about 5 dB increase in SMSR have been achieved experimentally. Furthermore, experimental results show that the wavelength spacing accuracy of the four-channel TS-DFB-LA can be improved by tuning the injection current of one of the two sections. Using the two-section structure, the dynamic characteristics including small-signal frequency response, relative intensity noise, and spurious-free dynamic range are also improved significantly. A radio-over-fiber link utilizing the TS-DFB laser as directly modulated light source was experimentally achieved. About 50 MSymbol/s 64-QAM signal with 10 GHz carrier was transmitted from the TS-DFB laser. After 40 km transmission in single-mode fiber, the average error vector magnitude of the whole link is 2.97%.

Large-Tolerant Direct Coupling to an SMF Array With a Lens-Integrated Surface-Emitting Laser

As a solution to provide a small-size and low-cost 100-Gb/s optical module, direct optical coupling between a lens-integrated surface-emitting DFB laser (LISEL) array and a single-mode fiber (SMF) array is demonstrated. A very-small far-field angle ( $\sim 2$ °) was obtained by monolithic integration of an InP lens with a laser chip. As a result, each channel of the LISEL array can directly couple to an SMF without any additional external optical components. The measured misalignment tolerance between the LISEL array and an SMF array was sufficiently large, namely, $\pm 5.5~\mu \text{m}$ , at excess loss of 1 dB over all four channels with the maximum coupling efficiency of 8.4 dB. These measurement results are in good agreement with a theoretical calculation based on Gaussian optics. These results demonstrate that high coupling efficiency (−3 dB) can be achieved while large misalignment tolerance ( $\pm 4.5~\mu \text{m}$ ) at excess loss of only 1 dB is maintained.

Integrated buried heterostructure DFB laser array for WDM systems based on reconstruction equivalent chirp technique

A distributed-feedback semiconductor laser array with buried heterostructure waveguide based on reconstruction equivalent chirp technique is experimentally demonstrated. The fabricated six-element laser array has channel spacing of 800 GHz and well meets the International Telecommunication Union standard, with relatively low threshold and high efficiency. Good single-longitudinal mode operation has been achieved at high injection current (120 mA) and high temperature (80°C), with side mode suppression ratios not lower than 40 dB, which is promising for the future wavelength division multiplexing systems. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1278–1281, 2015

Improved Single-Mode Property of DFB Semiconductor Laser Based on Sampling Technique Using Chirp Compensation

A DFB semiconductor laser with a bent waveguide and an equivalent chirp compensation based on the sampled grating technique is proposed to improve the single longitudinal mode (SLM) performance for the first time. In such a structure, the bent waveguide is used to form the basically chirped grating so that the zeroth-order resonance is greatly suppressed. However, for the $-$ first-order resonance, the equivalent chirp by designing the sampling pattern is used to compensate the chirp in the $-$ first subgrating caused by bent waveguide. As a result, the $-$ first-order resonance is enhanced, whereas the zeroth resonance is well suppressed. Since the wavelength spacing between the zeroth and $-$ first subgrating can be reduced by adopting this method, the sampling period can be increased. Therefore, the corresponding line in photomask can be enlarged as well to ease the fabrication, and the lasing wavelength accuracy can be further improved according to the theoretical analysis. Because the lasing wavelength can be controlled by changing the sampling period, the performances of the multiwavelength DFB laser array can also be improved using this method.

基于REC技术的可调谐DFB激光器阵列设计与测试

基于REC技术的可调谐DFB激光器阵列设计与测试

Fabrication of four-channel DFB laser array using nanoimprint technology for 1.3 μm CWDM systems

Four-channel monolithically integrated index-coupled distributed-feedback laser array has been fabricated using nanoimprint technology for 1.3 μm CWDM system. Selective lasing wavelength with 20 nm wavelength space is obtained. The present results show that the nanoimprint technology is mature and reliable in the fabrication of DFB laser array.

An equivalent-stepped-index-coupled DFB semiconductor laser and laser array realized by stepping the duty cycle of the Sampled Bragg grating

An equivalent-stepped-index-coupled (ESIC) distributed feedback semiconductor laser with an equivalent-stepped duty cycle (ESDC) is proposed and investigated numerically. The ESDC grating profile is realized by stepping the duty cycle of a Sampled Bragg grating (SBG) with the uniform seeding grating. Numerical results show that the light will be distributed in larger region along the laser cavity , that is to say, light field will be flattened and spatial hole burning can be suppressed in such flexible structure. Based on the ESDC structure, different sampling structures in a DFB laser array can also be obtained by stepping the sampling periods; therefore, multi-wavelength laser array can be designed and fabricated, which would simplify the fabrication process , and may be more suitable for the high precision and massive fabrication of DFB laser and laser array with reduced spatial hole burning. • We proposed an equivalent-stepped-duty cycle (ESDC) grating structure. • The ESDC profile is realized by stepping the duty cycle of a Sampled Bragg grating. • An equivalent-stepped-index-coupled (ESIC) DFB laser is based on the ESDC grating. • The SHB is suppressed effectively in the ESIC DFB laser. • The ESIC DFB laser array can be designed and fabricated easily based on the REC.

An Eight-Wavelength BH DFB Laser Array With Equivalent Phase Shifts for WDM Systems

In this letter, we report an eight-wavelength monolithically integrated buried heterostructure distributed feedback laser array with quarter-wave equivalent phase shifts. The laser array operating at 1.3 μm has a chip size of 2 mm × 250 μm. Lasing channel spacing is designed to be 800 GHz (~4.6 nm at 1.3 μm). The laser array exhibits accurate wavelength control and stable single mode lasing operation over a wide range of injection currents and different ambient temperatures. The measured linewidth of these lasers is 278 kHz at 65-mA bias current. In addition, the lasing wavelength of the whole laser array can be tuned continuously over 38.3 nm without mode hopping. The proposed method offers a practical approach of integrated laser array fabrication for wavelength-division multiplexing systems.

1.3-μm multi-wavelength DFB laser array fabricated by mocvd selective area growth

We report the fabrication of multi-wavelength DFB laser arrays operating around 1.3μm using a novel MOCVD based selective area growth approach. We show that the DFB laser wavelength can be precisely tuned by adjusting key design parameters including the oxide mask strip width and separation. Stable-single-mode DFB laser array operations are demonstrated with side mode suppression ratio >35dB and the wavelength span of DFB laser array can arrive at 13.9nm through optimizing the design parameters. Our process represents a simple and cost effective solution for applications requiring multi-wavelength laser sources covering a wide wavelength span, such as silicon photonic light sources in next generation 100G Gigabit Ethernet optical systems.

Erbium-doped waveguide DBR and DFB laser arrays integrated within an ultra-low-loss Si_3N_4 platform

Record low optical threshold power and high slope efficiency are reported for arrays of distributed Bragg reflector lasers integrated within an ultra-low-loss Si(3)N(4) planar waveguide platform. Additionally, arrays of distributed feedback laser designs are presented that show improvements in pump-to-signal conversion efficiency of over two orders of magnitude beyond that found in previously published devices. Lithographically defined sidewall gratings provide the required lasing feedback for both cavity configurations. Lasing emission is shown over a wide wavelength range (1534 to 1570 nm), with output powers up to 2.1 mW and side mode suppression ratios in excess of 50 dB.

Multichannel DFB Laser Arrays Fabricated by Upper SCH Layer SAG Technique

Multiwavelength laser arrays (MWLAs) fabricated by a novel upper separate confinement heterostructure (SCH) layer selective area growth (SAG) technique are studied in comparison with laser arrays fabricated by the conventional multiquantum well (MQW) SAG technique. For MWLAs by the MQW SAG, the range of the laser emission of the array is smaller than the span of the PL wavelengths of the MQW active layers. In addition, the material quality of the MQW layer degrades greatly as the width of the SAG strips is increased. Thus, the MWLAs fabricated by the method have scattered L-I characters and large fluctuation of wavelength spacings. In contrast, the MWLAs fabricated by the novel SAG method have much better wavelength spacing uniformity than those by MQW SAG, which is comparable to or better than the MWLAs fabricated by E-beam direct writing. Furthermore, the upper SCH layer SAG technique is suitable for the fabrication of MWLAs with wavelength interval, which is a challenge even for E-beam technique. In the SCH layer SAG, the MQW layer is untouched, and the same is true for all the laser elements in an array. The metal organic vapor phase epitaxies ability to control the material properties with high accuracy can be fully utilized for the fabrication of MWLAs. Combined with partially gain-coupled distributed feedback structures, the technique is promising for the fabrication of low-cost, high-quality MWLAs.

Study of the Multiwavelength DFB Semiconductor Laser Array Based on the Reconstruction-Equivalent-Chirp Technique

A detailed theoretical analysis of the lasing wavelength precision of the DFB laser array based on a reconstruction-equivalent-chirp (REC) technique is presented. Experimental results of the eight-wavelength DFB laser array with equivalent π phase shift (π-EPS) and four-wavelength DFB laser array with equivalent three shifts are also given. High lasing wavelength precision was obtained. This paper demonstrates that the REC technique is a promising way for fabricating the multiwavelength DFB laser array with low cost and high yield.

Sampled Grating DFB Laser Array by Periodic Injection Blocking

We present a novel multiwavelength laser array with a sampled grating formed by periodically loaded n-doped injection blocking layer on top of the uniform base grating. With an optimized design of the sampled grating as well as the laser operation conditions, all the even order, including the zeroth-order reflections, can be effectively suppressed, leaving only the first-order reflection wavelength to lase. Unlike in the conventional sampled grating where part of the base grating will have to be removed, the whole base grating is retained in the proposed structure; hence, the side-mode suppression ratio will not be jeopardized due to the weakened grating coupling strength. As an example, an array of 12 lasers has been designed to cover a wavelength range from 1542 to 1560 nm.

Experimental demonstration of a 16-channel DFB laser array based on nanoimprint technology

A 16-channel monolithically integrated index-coupled distributed-feedback laser array has been fabricated using nanoimprint technology. Selective lasing wavelengths with 300 and 100 GHz frequency space are obtained. The fine tenability for an individual laser in the array is achieved with a Ti–Au thin-film resistor integrated on the chip. The typical threshold current is between 10 and 15 mA without current in the thin-film resistor. The optical output power of each channel is about 6 mW at an injection current of 70 mA.