Jianjun Meng

Simple and compact V-cavity semiconductor laser with 50×100 GHz wavelength tuning

We report simple and compact V-cavity semiconductor laser capable of full-band wavelength tuning. A half-wave coupler is used to obtain high side-mode suppression ratio (SMSR) without any grating or epitaxial regrowth. Temperature induced gain spectrum shift is employed in combination with the Vernier tuning mechanism to extend the wavelength tuning range beyond the free spectral range limit. Wavelength tuning of 50 channels at 100GHz spacing with SMSR up to 38 dB has been demonstrated. We show that with a temperature variation of 35°C, the tuning range can be extended by about 15 nm, in contrast to 0.1 nm/°C for thermo-optic tuning range in grating based lasers. At a fixed temperature, consecutive wavelength tuning of 31 channels was achieved. The response time of the channel switching under the current-tuning regime is measured to be about 20μs. The large tuning range that can cover the full C-band will enable such a simple, compact and potentially low-cost tunable laser to be used in wavelength-agile access and data center networks.

All-optical flip-flop operation based on bistability in V-cavity laser.

We theoretically analyzed and experimentally demonstrated an injection-locking based all-optical flip-flop memory using a simple and compact tunable V-cavity laser (VCL). A bistable region in the tuning characteristics of the VCL is employed for the flip-flop operation. The state of the VCL can be set and reset by injecting signal pulses at two different wavelengths. The pulse power for both set and reset signal is only about 1 pJ. Short response times of about 150 ps are measured for storing and erasing.

Widely Tunable Semiconductor Laser Based on Double Half-Wave-Coupled Rectangular Ring Resonators

A widely tunable semiconductor laser based on double half-wave-coupled rectangular ring resonators is designed and simulated. By employing the Vernier effect between the rectangular ring resonators, a large tuning range of 40nm is achieved, while the corresponding threshold gain difference and the SMSR is 4.5cm-1 and 46dB, respectively.

Tunable V-coupled-cavity semiconductor laser monolithically integrated with monitoring photodiodes using deeply etched reflective trenches

We present a 1560-nm-band digitally wavelength tunable V-coupled-cavity semiconductor laser monolithically integrated with two waveguides based monitoring photodiodes (MPD) through deeply etched reflective trenches. The reflective trenches are designed to be 1.16μm wide, about three quarters of the wavelength, and are deeply etched through the waveguide with a depth larger than 4μm. Due to the high reflectivity of the etched trenches, a low threshold current of 19mA is achieved. Using a single electrode control, wavelength tuning of 22 channels at 100GHz spacing with SMSR above 35 dB is obtained. The relationship between the photocurrents of the two MPD at the two waveguide branches and the laser output power from the coupler side is investigated as a function of the wavelength. Since the integrated tunable laser with MPDs is very compact and does not involve any grating or epitaxial regrowth, it is suitable for low-cost multifunctional photonic applications for access and data center networks.

Full-band tunable V-cavity laser for low-cost access and data center networks

The principle, design and experimental results of widely tunable V-cavity lasers are reviewed. By using a novel half-wave coupler, single-mode lasing with high side-mode-suppression-ratio is achieved. Single-electrode controlled wideband wavelength tuning is realized by employing the Vernier mechanism. The tuning range can be further extended beyond the free spectral range limit by using the effect of temperature induced gain spectrum shift. The full-band tuning of 50 channels with 100 GHz spacing is demonstrated at 1550 nm range. Similarly, 41-channel tuning with 150 GHz spacing is achieved at 870 nm. The advantages of compactness, fabrication simplicity, and easy wavelength control offer great potential for the tunable laser to be used in low-cost access and data center networks.

Full C-Band Tunable V-Cavity-Laser Based TOSA and SFP Transceiver Modules

We report the latest development in tunable transmitter optical sub-assembly (TOSA) and small form-factor pluggable (SFP) transceivers based on simple and compact V-cavity laser (VCL), aiming for low-cost deployment in metro, access, and data center networks. The VCL employs a half-wave coupler to achieve high side-mode suppression ratio (SMSR) and the Vernier effect to achieve a wide wavelength tuning range. Full C-band tuning from 1529.55- to 1566.31-nm with SMSR above 36 dB is demonstrated. Since the laser does not involve any grating or epitaxial regrowth, and has a simple tuning algorithm, it allows simpler processes for fabrication and testing as compared with other widely tunable laser structures. Compact TOSAs and SFP transceiver modules have been developed for full C-band tuning with up to 93 channels at 50 GHz spacing. Transmission experiments are carried out for direct modulation with data rates from 2.5 to 8.5 Gbps. The results of reliability tests of the modules are also presented.

Wavelength Tunable V-Cavity Laser Employing Integrated Thin-Film Heaters

A wavelength tunable V-cavity laser (VCL) employing integrated thin-film heaters is reported. The laser is fabricated by a simple process with no grating or band-gap engineering. A single-electrode-controlled wavelength tuning of 32 channels is achieved by experiment, with a tuning efficiency of 0.13 nm/mW, which is about 1.5 times higher than that of the current injection based thermal tuning. By combining four single-electrode controlled tunings with different bias currents, we obtain 51 wavelength channels covering 43 nm. Well-open eye diagrams with extinction ratios above 6.6 dB are obtained in all channels under direct modulation at 2.5 Gbps. The power penalty over a 25-km fiber transmission is less than 0.3 dB. Clearly open eye diagrams with bit error rates (BERs) below 10-12 are also obtained at 5 and 8.5 Gbps after a 10-km single-mode fiber transmission.

Simple and compact tunable semiconductor lasers based on novel half-wave coupler

Widely tunable semiconductor lasers based on a novel half-wave coupler are presented. They have been implemented in the form of half-wave coupled V-cavity and ring-FP cavities. By using the novel half-wave coupler, single-mode lasing with high side-mode-suppression-ratio is achieved. Single-electrode controlled wide-band wavelength tuning with Vernier effect is demonstrated. The full-band tuning of 50 channels with 100GHz spacing is realized by further employing temperature induced gain spectrum shift. The laser is packaged into a small-form-factor 9-pin box TOSA, and the electronic driver has been developed for the wavelength tuning and direct modulation. The advantages of compactness, fabrication simplicity, easy wavelength control and direct modulation allow the tunable lasers to be used in low-cost access and datacenter networks, as well as in portable devices for spectroscopic analysis.

10Gb/s direct modulation of widely tunable V-cavity-laser with chirp managed laser technology

We report direct modulation results in a simple and compact widely tunable V-cavity laser. Chirp managed laser technology has been successfully applied to the V-cavity laser with an optical spectrum reshaping filter. The tunable V-cavity-laser employs a half-wave coupler to obtain single-mode operation with high side-mode suppression ratio and the Vernier effect to extend its tuning range. It does not require any grating structure and regrowth steps. In this experiment, we achieved single-electrode controlled wavelength tuning of about 18 channels at 100GHz spacing with a fixed temperature, and 32 channels using 2 temperature settings. Well-open eye diagrams with extinction ratio above 4.3dB in all channels are observed when the laser is directly modulated at 2.5Gb/s. Although the measured small-signal frequency response is only about 5.7GHz, more than 6.7dB extinction ratio under 10Gb/s modulation rate is achieved by using the chirp managed laser technology with an optical spectrum reshaping filter placed after the output of the laser to convert the frequency chirp accompanying the direct modulation to amplitude modulation. The advantages of compactness, fabrication simplicity, easy wavelength control algorithm, and simple direct modulation offer great potential for the chirped managed V-cavity laser to be used in low-cost WDM links.

Observation of negative frequency chirp in directly modulated tunable V-cavity laser

We report the observation of negative frequency chirp in directly modulated tunable V-coupled-cavity laser. At 2.5Gbps modulation rate with extinction ratio of 6dB, a negative chirp of 4.7GHz is measured. The mechanism of the negative chirp is explained by theoretical simulations of carrier dynamics in the V-cavity laser.