Tunable DBR Laser Research Articles

EAM Integrated Widely Tunable DBR Lasers Based on InGaAlAs/InP MQWs

EAM Integrated Widely Tunable DBR Lasers Based on InGaAlAs/InP MQWs

Enhanced direct modulation bandwidth in a tunable DBR laser with an equivalent phase shift grating

A high speed directly modulated and tunable distributed Bragg reflector laser is proposed based on an equivalent phase shift Bragg grating. By inserting a uniform waveguide in the middle of Bragg grating section, a notch is formed on reflectivity spectrum of the grating, and the photon-photon resonance (PPR) effect could then be introduced to extend modulation bandwidth. An independent electrode is also added for controlling the equivalent phase shift, which plays a key role in the design to introduce the PPR effects, and ensure compatibility with wavelength tuning. Stability, tunability and small signal response of the laser are numerically investigated, 40 GHz direct modulation bandwidth and 7 nm tuning range are obtained, indicating that the laser designed could achieve a large modulation bandwidth within a certain wavelength tuning range.

A Chirp-Managed Tunable DBR Laser Based on Novel Cascaded Gratings

In this paper, a novel tunable DBR laser based on novel cascaded gratings is proposed for chirp management in high-speed direct modulation applications. The cascaded gratings, i.e., a tilted π phase-shift grating followed by a normal uniform Bragg grating, can provide a narrow-band reflection spectrum with a sharp falling slope on the longer wavelength side, so that the optical spectrum shaping and the detuned-loading effects can be enhanced. Simulation results indicate that the wavelength tuning range of the laser is about 10 nm and the 3-dB modulation bandwidth reaches up to 25 GHz. By simply adjusting the phase current and thus changing the detuned frequency, the extinction ratio and the frequency chirp can be optimized, which is helpful to improve the dispersion tolerance and reduce the dispersion power penalty.

Wireless Data Transmission at Terahertz Carrier Waves Generated from a Hybrid InP-Polymer Dual Tunable DBR Laser Photonic Integrated Circuit

We report for the first time the successful wavelength stabilization of two hybrid integrated InP/Polymer DBR lasers through optical injection. The two InP/Polymer DBR lasers are integrated into a photonic integrated circuit, providing an ideal source for millimeter and Terahertz wave generation by optical heterodyne technique. These lasers offer the widest tuning range of the carrier wave demonstrated to date up into the Terahertz range, about 20 nm (2.5 THz) on a single photonic integrated circuit. We demonstrate the application of this source to generate a carrier wave at 330 GHz to establish a wireless data transmission link at a data rate up to 18 Gbit/s. Using a coherent detection scheme we increase the sensitivity by more than 10 dB over direct detection.

Temperature-Tolerant Wavelength-Setting and -Stabilization in a Polymer-Based Tunable DBR Laser

In this paper, we present a method of self-detection of mode hops in a distributed Bragg reflector tunable laser using the voltage drop in the active section as a monitoring signal. Based on this method, a wavelength setting and stabilization algorithm that is tolerant to temperature variations is proposed. Wavelength locking for a period of more than seven days with an accuracy better than ±1.25 GHz has been achieved, meeting the ITU-T standard for 25 GHz channel spacing. Under forced changes in the operation temperature from 15° to 60°, with variations of 0.1°/s, the maximum allowed deviation of ±2.5 GHz for the ITU-T standard with 50 GHz channel spacing was kept.

All-Optical Flip-Flop Operation in a Standard Tunable DBR Laser Diode

A novel concept for all-optical flip-flop operation in a distributed Bragg reflector laser is presented. Using pulses at the same wavelength but with a different duration and amplitude, flip-flop operation is obtained experimentally with switching times of 50 ps and pulse energies of 2-4 pJ.

Precompensation Techniques to Suppress the Thermally Induced Wavelength Drift in Tunable DBR Lasers

Wavelength drift caused by thermal transients is a major problem in optical routers which use semiconductor tunable lasers for packet switching. Wavelength drift is induced by the temperature variations in laser sections caused by switching of the tuning currents. A thermal model is used to analyze the optical frequency drifts due to the thermal characteristics of the laser chip and its mount. We investigate the impact of thermal effects on switching behavior of a three-section distributed Bragg reflector laser and show numerically that the wavelength drift can be counteracted by using precompensation of passive section currents. Results from numerical simulation show that the wavelength drifts can be suppressed by more than 80%.

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.

Selective-area MOVPE growth for 10 Gbit/s electroabsorption modulator integrated with a tunable DBR laser

We have designed and fabricated electroabsorption modulator integrated monolithically with a distributed Bragg reflector laser using selective area growth (SAG) by metalorganic vapor phase epitaxy (MOVPE). Through the bandgap engineering due to the growth rate enhancement and compositional variation from the difference of migration and/or diffusion length of species by various SAG mask pattern, we have achieved the photoluminescence peak wavelengths of active layer in the laser, modulator, and Bragg grating regions to 1.557, 1.503, and 1.442 μm, respectively. The electroabsorption modulator-integrated laser shows a good performance including threshold current of below 6 mA, output power of 5 mW for 45 mA current injected in the active region, and high side-mode suppression ratio over 45 dB with the 3-dB modulation bandwidth over 11 GHz.

A widely tunable SOA-integrated DBR laser by combination of sampled and superstructure gratings

We report on the development of the first 30 nm tunable laser diode utilizing a front sampled grating-distributed Bragg reflector (SG-DBR) and a rear superstructure grating DBR (SSG-DBR). A high output power greater than 18 mW was achieved with superior longitudinal mode stability, as well as an overall power variation of less than 3 dB for the well-defined laser. Furthermore, lasers integrated with a semiconductor optical amplifier (SOA) enabled the output power to be controlled independently both by the active current and the SOA current, as well as achieving a maximum output power of 45 mW. The side-mode suppression ratio was in excess of 40 dB for all the 50 GHz spaced wavelength channels.

40-GHz dual-mode-locked widely tunable sampled-grating DBR laser

Generation of 40-GHz alternate-phase pulses is demonstrated using a dual-mode-locked sampled-grating distributed Bragg reflector laser. More than 10-dB extinction and >20-dB sidemode suppression ratio is measured over the >40-nm tuning range of the laser. Based on captured phase noise spectra, the timing jitter is estimated in the 0.35-0.41-ps range. The demonstrated dual-mode laser would form an attractive basis for an integrated 40-Gb/s return-to-zero transmitter.

Realization of Phase Grating Comb Reflectors and Their Application to Widely Tunable DBR Lasers

Widely tunable InP lasers often require comb reflectors as an integral part of their design. It is desirable to achieve comb reflectors with as "top-hat" like a response as possible. There are several ways to do this, but one simple and practical way is by utilizing a phase grating. Previously these have been discussed theoretically, but here we will describe the fabrication of such gratings and how they can find application as the reflectors in widely tunable InP lasers. The example devices which we will discuss show that phase-grating-based distributed Bragg reflector lasers can have tuning ranges of around 35 nm combined with excellent sidemode suppression ratio of better than 45 dB at the mode centers.

Single-Chip Wavelength Conversion Using a Photocurrent-Driven EAM Integrated With a Widely Tunable Sampled-Grating DBR Laser

Tunable photocurrent-driven wavelength converters using widely tunable sampled grating distributed Bragg reflector lasers, electroabsorption modulators, semiconductor optical amplifiers, and an optically preamplified receiver have been fabricated and tested. Dynamic wavelength conversion has been achieved over 40 nm with optical bandwidths up to 10 GHz.

Widely tunable electroabsorption-modulated sampled-grating DBR laser transmitter

We report on a widely tunable transmitter based on a sampled-grating distributed Bragg reflector (SG-DBR) laser monolithically integrated with a semiconductor optical amplifier (SOA) and an electroabsorption (EA) modulator. Modulated time-averaged powers in excess of 5 dBm, RF extinction ratios >10 dB, and error-free transmission at 2.5 Gb/s for 350 km of standard single-mode fiber have been demonstrated across a 40-nm tuning range. In CW mode of operation, the module meets all long-haul system requirements for externally modulated laser sources: stability, power (>10 mW), RIN ( 100 yr for output wavelength stability and power across all channels.

Tunable sampled-grating DBR lasers using quantum-well intermixing

Widely tunable lasers are key components for wavelength division multiplexing fiber optic networks. They reduce cost in sparing, enable dynamic networking applications, and present opportunities for future monolithically integrated wavelength division multiplexing components. The sampled-grating distributed Bragg reflector (SGDBR) laser is ideal for these purposes. The authors present a centered quantum-well SGDBR laser which uses quantum-well intermixing in order to improve device characteristics over previous designs. The mode overlap is improved by 50% over the offset quantum-well design, improving the modal gain. Current injection tuning in the intermixed material is demonstrated for the first time; the maximum modal group index change was measured to be 1%.

Relative intensity noise measurements of a widely tunable sampled-grating DBR laser

The intensity noise of a sampled-grating distributed Bragg reflector laser with 50-nm tuning range and 45-dB side-mode suppression ratio has been measured. The resonance frequency, damping factor, and modified Schawlow-Townes linewidth are extracted from the noise spectra. At high output power, the relative intensity noise (RIN) of the laser is below the photodiode shot noise limit, which is -160 dB/Hz. The laser has uniform shot noise limited RIN properties along the whole tuning range. The maximum resonance frequency is 5.4 GHz at a bias current of 120 mA and the K factor is 0.58 ns.

Dynamic range of widely tunable sampled-grating DBR lasers

The dynamic range of sampled-grating distributed Bragg reflector lasers is investigated. The system noise is limited by the photodiode shot noise, which is below −160 dBm/Hz at normal bias current. The spur-free dynamic range is between 100–112 dB · Hz2/3. Both the noise and linearity are uniform over the whole tuning range of 50 nm, and are relatively insensitive to mode detuning.

Novel interleaved sampled grating mirrors for widely tunable DBR lasers

Novel sampled grating mirrors with interleaved gratings (ISGs) are proposed for the realisation of widely tunable DBR lasers based on the Vernier principle. The ISG design parameters used to control the spacing of the peaks and the shape of the maximum reflectivity envelope are presented in a design example of a widely tunable DBR laser. The simulated performances of ISG-DBR are compared with those of a sampled grating-DBR laser with the same length and the same maximum reflectivity for each mirror. The advantages gained from interleaving are discussed, paying particular attention to the static characteristics in the tuning range. It is shown that ISGs limit the threshold current variations in the coarse tuning operation mode because of the flatter envelope of the reflectivity maxima and can be useful to reduce the output power variations in the continuous tuning operation mode.

120 mW tunable DBR lasers emitting at 1060 nm

High power, continuously tunable three-section DBR diode lasers with an output power of 124 mW at 200 mA pump current are presented. Continuous tuning over more than 300 GHz with a frequency of 100 Hz is achieved due to heating of narrow resistors above the passive sections.

Tunable distributed Bragg reflector laser-electroabsorption modulator based on identical active layer monolithic integration approach

The monolithic integration of a tunable DBR laser and electroabsorption modulator is reported. A common strained multiquantum well active layer is used for the three optical functions of this device. A tuning range of 7.4 nm and an extinction ratio higher than 12 dB for all the eight accessible channels are reported at 1.55 µm.