Tunable Sampled-grating Distributed Bragg Reflector Research Articles

Numerical Analysis on Thermal Tuning Efficiency and Thermal Stress of a Thermally Tunable SG-DBR Laser

Thermally tunable sampled grating distributed Bragg reflector (SG-DBR) lasers are very attractive for applications of optical coherent systems, where light sources with narrow linewidth are key requirements. In this paper, we focus on the thermal tuning efficiency and the thermal stress field of such lasers. The influence of a thermal isolation (air trench) design on the tuning efficiency of the laser is analyzed by using a thermal model based on the finite-element method (FEM) at first. The thermal tuning efficiency is found to be tenfold improved if the air trench is used. Influences of the air trench geometry configurations on temperature and thermal stress field are then examined in detail. Simulation results indicate that the most dangerous positions that can crack always appear at the output port and the corner of the air trench structure contact with the n-InP layer. The air trench geometry configuration of an SG-DBR laser is finally optimized (with a width of 70 $\mu\text{m}$ and a thickness of 1 $\mu\text{m}$ ) to ensure the reliability and the quasi-continuous wavelength tuning range of the device at the same time. With the optimized design, by using a developed temperature-dependent transfer matrix method-based optical model, optical output characteristics of the thermally tunable SG-DBR laser are demonstrated, including the output wavelength for the tuning range (1525–1585 nm covering C band) and the linewidth for all the channels (several tens to several hundreds of kilohertz). The simulated results have been found to be in good agreement with the experimental measurements previously reported, which are helpful to the thermal management and the design optimization of such devices.

Two-Dimensional Optical Beam Steering With InP-Based Photonic Integrated Circuits

Two-dimensional optical beam steering using an InP photonic integrated circuit has been demonstrated. Lateral beam steering controlled by a 1-D phased array has been made easier through on-chip interferometer monitors. Longitudinal beam steering controlled by the input wavelength has demonstrated an efficiency of 0.14 °/nm. Very fast beam steering (>107 °/s) in both dimensions has been demonstrated as well. As the latest development, a widely tunable sampled-grating distributed Bragg reflector laser has been monolithically integrated and 2-D beam steering has been demonstrated with this on-chip tunable laser source.

Modeling of Tunable DBRs Lasers Based on Transmission-Line Laser Model

The transmission-line laser model (TLLM) is extended to simulate the three-section distributed Bragg reflector (DBR) lasers, while a combined model of TLLM and digital filter approach is developed to study the sampled grating DBR (SGDBR) lasers. We integrate time-domain TLLM method and frequency-domain transfer matrix method (TMM) in the combined model. Characteristics of tunable DBR lasers and SGDBR lasers are all successfully simulated, such as L-I curve, and static tuning characteristics, which are in good agreement with the published experimental results. This new method is also used to study transient response and lasing spectrum of the devices, which are difficult to be obtained by the frequency domain models.

An 8$\,\times\,$8 InP Monolithic Tunable Optical Router (MOTOR) Packet Forwarding Chip

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, we demonstrate single-channel operation of the first InP monolithic tunable optical router (MOTOR) chip designed to function as the packet forwarding engine of an all-optical router. The device has eight-input and eight-output ports and is capable of 40-Gb/s operation per port with bit-error rates below 1E-9. MOTOR integrates eight wavelength-tunable differential Mach–Zehnder semiconductor optical amplifier (SOA) wavelength converters with preamplifiers and a passive 8<formula formulatype="inline"><tex Notation="TeX">$\,\times\,$</tex> </formula>8 arrayed-waveguide grating router. Each wavelength converter employs a widely tunable sampled-grating distributed Bragg reflector (DBR) laser for efficient wavelength switching across the C band and other functions required for 40-Gb/s wavelength conversion. Active and passive regions of the chip are defined through a robust quantum well intermixing process to optimize the gain in the wavelength converters and minimize the propagation losses in passive sections of the chip. The device is one of the most complex photonic integrated circuits (PICs) reported to date, with dimensions of 4.25 mm<formula formulatype="inline"><tex Notation="TeX">$\,\times\,$</tex></formula>14.5 mm and more than 200 functional elements integrated on-chip. We demonstrate single-channel wavelength conversion and channel switching with this device using <formula formulatype="inline"><tex Notation="TeX">$2^{31}-1$</tex></formula> pseudorandom bit sequence (PRBS) data at 40 Gb/s. A power penalty as low as 4.5 dB was achieved with less than 2-W drive power per channel. </para>

Investigation on wavelength switching of widely tunable SGDBR lasers

The sampled-grating distributed Bragg reflector (SGDBR) laser is a typical and important photonic integrated device, and has potential wide application to agile optical networks. A new dynamic model for this device has been developed, which combines the traveling-wave method for the active region and the transfer-matrix method for the passive sections into a single procedure. The behaviors of wavelength switching of the SGDBR laser, which include the transient spectrum and mode competition, have been studied in detail using this model. A new efficient way has been proposed to improve the wavelength switching performance only by increasing the coupling coefficients without changing the carrier density.

Modeling Widely Tunable Sampled-Grating DBR Lasers Using Traveling-Wave Model With Digital Filter Approach

A theoretical model for simulating widely tunable sampled-grating distributed Bragg reflector (SGDBR) lasers has been developed. The model integrates both time-domain traveling-wave method and frequency-domain transfer-matrix method into a single procedure. The active region of the device is still operated in the conventional time domain, while the passive parts are firstly performed by the transfer-matrix method and then transformed to the time domain via digital filters. Both the static and dynamic characteristics of SGDBR lasers, such as L-I curve, output spectrum, tuning characteristics, large-signal modulation, and dynamic wavelength switching, can be clearly visible in our model and in qualitative agreement with the published experimental results.

Modeling Wavelength Switching of Widely Tunable Sampled-Grating DBR Lasers Using Traveling-Wave Model With Digital Filter Approach

A dynamic theoretical model has been proposed for simulating the wavelength switching performance of widely tunable sampled-grating distributed Bragg reflector lasers. The active region of the device is still operated in time domain while the passive parts are first modeled by transfer-matrix method and then transformed into the time domain via digital filter approach. The switching performance and corresponding mode-competition behaviors can be clearly demonstrated by the transient spectrum traced by the switching time.

A Monolithic All-Optical Push–Pull Wavelength Converter

We present the first two-stage all-optical push-pull wavelength converter, which has been monolithically integrated in indium phosphide, using an offset quantum-well platform. The device incorporates two cascaded wavelength converters, each with an integrated tunable sampled-grating distributed Bragg reflector laser, and deeply etched total internal reflection mirrors for a compact layout. The device, under push-pull operation, is demonstrated to reduce converted signal pattern dependence at 10 Gb/s, while providing improved phase swing compared to previous offset quantum-well designs. The device is shown to achieve full pi phase swing in the second-stage wavelength converter over a 12-dB input power range.

Performance optimization of an InP-based widely tunable all-optical wavelength converter operating at 40 Gb/s

We report on the design and performance optimization of a quantum-well active region-based semiconductor optical amplifier Mach-Zehnder interferometer wavelength converter monolithically integrated with a widely tunable sampled-grating distributed Bragg reflector laser, operating differentially at 40 Gb/s. The device is fabricated using an offset quantum-well platform, requiring a single regrowth. We show error-free operation, with a less than 3-dB power penalty at the optimal differential delay, and open eyes across a 25-nm output tuning range.

Postgrowth control of the quantum-well band edge for the monolithic integration of widely tunable lasers and electroabsorption modulators

We describe a quantum-well intermixing process for the monolithic integration of various devices, each with a unique band edge. The process involves a single ion implant followed by multiple etch and anneal cycles. We have applied this method to design and fabricate widely tunable sampled-grating distributed Bragg reflector lasers with integrated electroabsorption modulators. The devices employ three unique band edges, and demonstrate exceptional tuning, gain, and absorption characteristics.

Direct intensity modulation in sampled-grating DBR lasers

In this letter, we present new experimental results obtained for direct intensity modulation of widely tunable sampled-grating distributed Bragg-reflector (SGDBR) lasers. These results are of significance to SGDBR applications in wavelength-division-multiplexing systems. The devices described operate in the C-band (wavelength range 1525-1565 nm). A 6-GHz small-signal modulation bandwidth and >10-dB signal extinction ratio under large-signal operation were obtained. We have also recorded an undistorted eye pattern for a nonreturn-to-zero random signal 2/sup 31/-1 word length at 2.5-Gb/s bit rate during transmission over 75-km of standard single-mode fiber.

Directly modulated sampled grating DBR lasers for long-haul WDM communication systems

The limitations on high-speed data transmission, using widely tunable sampled-grating distributed Bragg reflector (SGDBR) lasers, are investigated. We demonstrate 1.244-Gb/s data transmission over a wavelength range of 45 nm using a single directly modulated tunable SGDBR laser diode. Data transmission was evaluated on four separate wavelength channels each spaced 15 nm apart. Less than 0.6 dB of dispersion penalty was measured on all four channels for transmission over 50 km of standard single-mode optical fiber.