A Widely Tunable Three-Section DBR Lasers for Multi-Species Gas Detection

Wavelength tunable and directly modulated distributed Bragg reflector (DBR) lasers with butt-joint technology are designed, fabricated and characterized. The DBR laser consists of a gain section and a DBR section. To increase the electrical isolation between the gain section and the DBR section, parts of a p-doped material in the isolation region are etched off selectively. Over 2 kΩ isolation resistance is realized ultimately without the need of ion implantation, which simplifies the fabrication process. The laser exhibits high speed modulation with a large tunable range. The 3 dB direct modulation bandwidth of the device is over 8 GHz in a 12 nm tunable range. This widely tunable DBR laser with the simple structure is promising as a colorless light source for the next-generation time and wavelength division multiplexed passive optical network (TWDM-PON) systems.

A preliminary design for a broadband, multiple quantum well (MQW), distributed Bragg reflector (DBR), electronically tunable laser diode array has been developed for implementation into optical memory configurations. The proposed MQW DBR diode array and a waveguide hologram with a blazed grating and/or holographic diffraction grating will be integrated into a photonic random optical memory access (PROMAC) device. PROMAC is a low inertia, low power, sub-nanosecond, parallel (e.g. 64 bit wide), wavelength addressing device which exploits free space optical interconnects. The MQW DBR laser diode array will enhance the performance of PROMAC by offering advantages in speed, spectral resolution, holographic separation and scan efficiency. An increase in speed as well as a decrease in power consumption can also be realized. Thus, increased storage densities and faster access rates can be achieved.

A theoretical model for two- and three-section tunable distributed Bragg reflector (DBR) lasers is presented. The static tuning properties are studied in terms of threshold current, linewidth, oscillation frequency, and output power. Regions of continuous tuning for three-section DBR lasers are presented. Different routes for continuous tuning, when the injection currents to the passive sections are varied, are discussed and the limitations on the continuous tuning range are clarified. By proper control of these currents, a tuning range of approximately 400 GHz is predicted at 1.55 mu m wavelength, which is in good agreement with the experimental results published thus far.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A GaAsP quantum well tunable distributed Bragg reflector (DBR) laser with a thin-film heater above a DBR grating was designed and fabricated. As a result of the optimization of the DBR grating to obtain both high reflectivity and sharp wavelength selectivity, single-mode lasing with an output power of 54 mW and a side-mode suppression ratio of 43 dB was obtained. By forming the transparent thin-film heater at a distance of 0.1 µm above the DBR grating, the DBR grating was heated locally and efficiently, and a wide wavelength tuning range of 5.2 nm was achieved by heating with a heater power as low as 160 mW.

We report 20 Gb/s transmission of four-level pulse amplitude modulation (PAM) signal using a directly modulated tunable distributed Bragg reflector (DBR) laser. Transmission distance over 20 km was achieved without using optical amplifiers and optical dispersion compensation modules. A wavelength tuning range of 11.5 nm and a 3 dB bandwidth greater than 10 GHz over the entire wavelength tuning range were obtained.

Quantum dot (QD) lasers epitaxially grown on Si have already been demonstrated to show record low threshold, high temperature tolerance, and low feedback sensitivity. When grown on the silicon photonic chip and integrated with Si waveguides (WGs), QD lasers offer considerable economical and foundry‐scalable solutions to on‐chip light sources. Yet, a technology that enables both growth and integration of QD lasers on a silicon photonic chip has not been demonstrated. Herein, a novel device platform which enables integration of the QD active region with passive WG structures is designed. By doing so, complex and high‐performance lasers such as distributed Bragg reflector lasers, mode‐locked lasers, and sampled grating distributed Bragg reflector tunable lasers are demonstrated in this platform. The same laser epitaxial stack can be easily grown on the substrate of a silicon photonic chip to allow light coupling from QD laser cavities to the silicon WGs.

Tunable laser diodes are now widely used in dense wavelength division multiplexing (DWDM) optical fiber networks. A wide tunability range and good frequency stability are generally required, without mode hopping. Special applications require fast frequency measurement. Unfortunately, commercially available classical spectral measurement systems are much too slow for that purpose. In this paper, we present a new and low-cost system dedicated to fast spectral measurements based on a Michelson interferometer. The free spectral range (FSR) of the interferometer must be carefully optimized. We have designed optimized and tested an experimental system that can quickly analyze with good accuracy the tunability range of tunable distributed Bragg reflector (DBR) laser diodes, and their possible mode hopping. Our set-up can also be used for other spectral measurements (linewidth, chirp, Henry's alpha enhancement factor, spectral and power monitoring). After theoretical analysis of our experimental set-up, we finally present the fast spectral measurements results obtained with a typical 1550 nm two sections DBR QW (quantum well) laser diode. Our measurements have been obtained within less than 500 ps, which is much faster than limits induced by switching thermal effects in laser diodes, and that speed could still be increased.

Wavelength tunable electro-absorption modulated distributed Bragg reflector lasers (TEMLs) are promising light source in dense wavelength division multiplexing (DWDM) optical fiber communication system due to high modulation speed, small chirp, low drive voltage, compactness and fast wavelength tuning ability. Thus, increased the transmission capacity, the functionality and the flexibility are provided. Materials with bandgap difference as large as 250nm have been integrated on the same wafer by a combined technique of selective area growth (SAG) and quantum well intermixing (QWI), which supplies a flexible and controllable platform for the need of photonic integrated circuits (PIC). A TEML has been fabricated by this technique for the first time. The component has superior characteristics as following: threshold current of 37mA, output power of 3.5mW at 100mA injection and 0V modulator bias voltage, extinction ratio of more than 20 dB with modulator reverse voltage from 0V to 2V when coupled into a single mode fiber, and wavelength tuning range of 4.4nm covering 6 100-GHz WDM channels. A clearly open eye diagram is observed when the integrated EAM is driven with a 10-Gb/s electrical NRZ signal. A good transmission characteristic is exhibited with power penalties less than 2.2 dB at a bit error ratio (BER) of 10^-10 after 44.4 km standard fiber transmission.

The mechanisms of wavelength tuning in the multisection distributed feedback (DFB) and distributed Bragg reflector (DBR) lasers are discussed and a review is made of recent progress. It is shown that the maximum wavelength tuning range is limited by the maximum refractive index change in a semiconductor.

This paper presents a theoretical and experimental study of nonlinear effects in distributed Bragg reflector (DBR)-type tunable lasers, which are responsible for asymmetric spectral or power characteristics, and for hysteresis phenomena. We propose an optimized DBR semiconductor optical amplifier design that suppresses these effects, making the control simpler and more reliable, while maintaining the same performances as a DBR (16 nm tuning, 40 dB side mode suppression ratio, 20 mW coupled output power). Aiming to reach C-band tuning range with only one Bragg current control and reduced nonlinear effects, a new double Bragg DBR laser is proposed.

A high power SHG blue laser with direct modulation capability at high frequency has been demonstrated usinga tunable distributed Bragg reflector (DBR) laser diode and a waveguide-type quasi-phase-matched secondharmonic generation (QPM-SHG) device in x-cut Mg doped LiNbO3. Continuous blue light power of 12 mWand pulsed peak power of 26 mW were generated. The SHG blue laser was installed to an optical head, andreadout of ROM disk and recording on phase change optical disk were performed. A butt-coupling-type 0.8cc SHG blue laser was also fabricated. It was indicated that SHG blue laser is applicable to high-density opticaldisk system.

For accurate control of the channel spacing in fabricating multiwavelength laser arrays or discrete multicolor lasers, we proposed a novel approach that exploits sampled grating distributed Bragg reflector (DBR) mirrors to vary the laser wave length across the wafer. This approach can realize a set of lasers with a wavelength spacing that meets the ITU recommendations for dense wavelength-division multiplexing systems and a wavelength range that can cover up to 40 nm or more. The wavelength variation across an array is achieved by changing the sampling periods of the DBR mirrors from laser to laser. The accuracy on the channel spacing of sampled grating DBR laser arrays was shown to be the same as that of conventional distributed feedback or DBR laser arrays, but their wavelengths can be better controlled for the gratings are fabricated with single holographic exposure. Arrays of 21 lasers have been successfully fabricated and have around 0.8-nm wavelength spacing with a simple tuning mechanism.

Intensity modulation characteristics of a 1.5- mu m butt-jointed DBR (distributed-Bragg-reflector) laser with wavelength tuning were studied. A 3-dB modulation bandwidth of 9 GHz and a high relaxation oscillation frequency of more than 10 GHz were obtained for the DBR laser. These characteristics were not affected by changing the lasing wavelength. The chirping width of the DBR laser is lower than that of the distributed feedback (DFB) laser. A clear eye opening and low chirping characteristics were obtained under 5-Gb/s nonreturn to zero (NRZ) pseudorandom modulation with a sufficient extinction ratio.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Threshold current density and differential quantum efficiency are analyzed for a surface emitting (SE) lambda /4-shifted distributed feedback (DFB) laser consisting of alternating active and passive layers with a distributed Bragg reflector (DBR). It is shown that the threshold current density can be reduced by using the DFB action induced by alternating active and passive layers in the active region of the SE DFB laser structure, as compared to SE DBR lasers with a homogeneous active region. It is also shown that the differential quantum efficiency of the DFB laser with a DBR can be higher than that of conventional DBR lasers without increasing the threshold current density. >

A novel magnetic field sensor using distributed Bragg reflector (DBR) fiber laser by Ampere’s force effect is proposed and experimentally demonstrated. The key sensing element, that is the dual-polarization DBR fiber laser, is fixed on the middle part of two copper plates which carry the current. Ampere’s force is applied onto the coppers due to an external magnetic field generated by a DC solenoid. Thus, the lateral force from the coppers is converted to a corresponding beat frequency signal shift produced by the DBR laser. The electric current sensing is also realized by the same configuration and same principle simultaneously in an intuitive manner. Good agreement between the theory calculation and the experimental results is obtained, which shows a good linearity. This sensor’s sensitivity to the magnetic field and to the electric current finally reaches ~258.92 kHz/mT and ~1.08727 MHz/A, respectively.