Distributed Bragg Reflector Semiconductor Laser Research Articles

Generation of optical frequency combs by Q-switching integrated multi-section semiconductor lasers.

In this work we perform a theoretical and simulation analysis of the behavior of an integrated four section distributed Bragg reflector semiconductor laser under optical injection and Q-switching operation. An electro-absorption modulator is introduced into the laser cavity to control the total losses and perform Q-switching. The simulations are done using a rate equation model. Q-switching operation produces very short and high power pulses. This, together with the use of optical injection, allows obtaining flat and broad optical frequency combs with up to 2100 optical lines within 10 dB (642 lines within 3 dB) at a repetition frequency of 100 MHz. The high chirp of the pulses is responsible for the broad spectra of these combs in comparison with gain switched combs, and the device structure allows fabrication in commercial foundries using standard building blocks.

Design of Grating Structure in Distributed Bragg Reflector Semiconductor Laser

Design of Grating Structure in Distributed Bragg Reflector Semiconductor Laser

Hybrid algorithm for predicting the temperature-variation-induced wavelength drift of DBR semiconductor lasers.

In this paper, a hybrid algorithm to predict the wavelength drift induced by ambient temperature variation in distributed Bragg reflector semiconductor lasers is proposed. This algorithm combines the global search capability of a genetic algorithm (GA) and the supermapping ability of an extreme learning machine (ELM), which not only avoids the randomness of ELM but also improves its generalization performance. In addition, a tenfold cross-validation method is employed to determine the optimal activation function and the number of hidden layer nodes for ELM to construct the most suitable model. After applying multiple sets of test data, the results demonstrate that GA-ELM can quickly and accurately predict the wavelength drift, with an average rms error of 4.09×10-4nm and average mean absolute percentage error of 0.21 %. This model is expected to combine the temperature and current tuning models for a wavelength in follow-up research to achieve rapid tuning and high stability of a wavelength without additional devices.

High Power Distributed Bragg Reflector Lasers at 689.45 nm for Quantum Technology Applications

Distributed Bragg Reflector semiconductor lasers are ideally suited for quantum technology applications due to their high efficiency, small footprint, and tunability in combination with the frequency stability provided by an integrated frequency selective element. Here we present the design, fabrication, and electro-optical characterization of DBR lasers optimized for strontium-based quantum technology applications at 689.449 nm. The devices achieved an optical output power of up to 88 mW, four times more than previously reported, as well as a spectral linewidth of 0.4 MHz.

Investigation of red‐emitting distributed Bragg reflector lasers by means of numerical simulations

The authors report theoretical and experimental results on the properties of distributed Bragg reflector semiconductor lasers. Using the traveling wave equation model, they show that a proper choice of coupling coefficient and front facet reflectivity allows an optimisation of the laser operation, such that for wide range of injected current into the active region the laser emits a temporally stable output power. The numerical results are in a qualitative agreement with the measured characteristics.

Guest Editorial

It is a great pleasure for me to introduce this Special Issue of IET Optoelectronics, which is focussed on semiconductor optical devices. Once a year, a Special Issue on this topic is published in association with the Semiconductor and Integrated OptoElectronics (SIOE) conference held in Cardiff, UK. In 2016 SIOE celebrated its 30th anniversary and as always, featured an exciting programme with a very high standard of technical talks, some of which feature as extended versions in this issue. Semiconductor optoelectronics is constantly evolving with the emphasis on integration continuing to grow as a key theme, in both materials and device functions, and this is largely to meet the demand of technological trends. The push for photonic integrated systems and ‘smart’ devices is setting the scene for research and such systems are predominately designed with energy efficiency in mind. In the context of this field, so called ‘green photonics’ has a great importance for society and naturally promotes high impact for research proposals, which is particularly beneficial given the competitive nature of funding. In this issue, we showcase some of the key papers featured at SIOE, giving you a flavour of the subject areas of the conference sessions, many of which relate to the trends identified above. On the topic of green photonics, there are two papers concerning the development of solar cells: Wang, Q. et al. make use of a detailed balance model to investigate enhancing the efficiency of intermediate band solar cells by introducing carrier losses and compare this with the effect of using alloying and biaxial strain. Cappelluti, F. et al. present research on open-circuit voltage recovery in quantum dot solar cells. A numerical study is used to investigate the effect of wetting layer states and doping on the photovoltage loss in InAs/GaAs solar cells.This includes quantum mechanical simulations to analyse how the reduction of the wetting layer by overgrowth can influence the quantum dot states. It is an exciting and busy time for researchers in the area of terahertz (THz) technology, this relatively untapped region of the electromagnetic spectrum promises a plethora of applications, in medicine, quality-control and detection of explosives, to name a few. Low-cost, energy efficient ways to emit THz radiation using semiconductor optical devices is fast becoming a realistic prospect for commercial applications and will surely be a ubiquitous technology in the near future. THz research featured prominently at the conference with two papers included in the Special Issue: firstly Gwaro, J. et al. report on the implementation of a cost-effective compact THz source, which features a monolithically integrated dual-wavelength distributed Bragg reflector (DBR) semiconductor laser diode, making use of photo-conductive antennas. Secondly, Wang, Y. et al. describe their research on THz photoconductive antennas using low-temperature grown III-V compounds which incorporated DBRs to enhance the THz peak signal. Characterisation of novel laser devices and materials always forms a large part of the SIOE conference, through both experimentation and modelling. Modulation and tuneability of lasers formed a key topic area, as well as mode-locking and dynamic behaviour. Dugzul, O. et al. investigated the effect of optical-injection-locking on modulation dynamics of tuneable laser diodes and a travelling wave approach, making use of an integrated VPI, and PICS3D commercial software was used to assess the dynamic response of a three-section InGaAsP/InP tuneable laser. Tawfieq, M. et al. discuss the concept of numerical simulations of a widely tuneable 4-section sample-grating laser, emitting at 976 nm, and present data on the accessible wavelength range, the threshold current behaviour and gain characteristics. Experimental results, from monolithic colliding-pulse mode-locked lasers, containing chirped double-quantum-well active regions are reported by Prziwarka T. and co-workers. They discuss factors such as gain current, absorber length/voltage, and compromises made to achieve short (picosecond) pulses with relatively low repetition frequencies. Finally, our invited paper by Kellehur, B. et al. theoretically investigates an experimental phenomenon observed between mutually coupled quantum dot lasers, which exhibit a greatly reduced modal linewidth when mutually phase-locked. I thank the authors who contributed fully expanded papers for the Special Issue and I would also like to thank the referees for their time spent reviewing manuscripts and forming constructive comments. Now I shall leave you to enjoy reading this selection of papers and hope to see you all at future SIOE conferences. Dr. Samuel Shutts is a Research Associate in the School of Physics and Astronomy at Cardiff University. He is involved with the design, fabrication and characterisation of semiconductor light emitting devices. His current research interests include quantum dot lasers structures grown on silicon substrates; InP/AlGaInP quantum dot lasers; dual-wavelength sources; distributed Bragg reflectors and distributed feedback lasers and THz emission via difference frequency generation.

Terahertz frequency generation with monolithically integrated dual wavelength distributed Bragg reflector semiconductor laser diode

Optoelectronic terahertz (THz) generation techniques have helped to narrow the THz gap and have opened up a wealth of new applications for THz technology. However, the development of THz systems into mass market is a major technical challenge, which is attributed to high cost of THz hardware components including sources and detectors. Here, the authors report THz generation from a distributed Bragg reflector (DBR) semiconductor laser diode together with fibre coupled photoconducting antennas. Two fibre coupled ion-implanted gallium arsenide photoconducting antennas were employed to generate and detect THz radiation. Two DBR lasers connected with a Y-shaped waveguide structure were monolithically integrated and used to simultaneously emit two wavelengths in the range of 785 nm. These lasers were employed as pumping source for the photomixers. An optical beat frequency of 286 GHz of the dual wavelengths was obtained from optical characterisation. A corresponding THz frequency was confirmed via photomixing in a homodyne set up. By variation of the operation parameters of the laser, the difference frequency was tuned in the range between 286 GHz to 320 GHz. In summary, they report the implementation of a compact and cost effective fiber coupled Terahertz source based on a monolithically integrated dual wavelength DBR semiconductor laser diode.

Narrow Linewidth Surface-Etched DBR Lasers: Fundamental Design Aspects and Applications

Surface-etched distributed Bragg reflector (SE-DBR) semiconductor lasers show potential for use in a variety of communications and spectroscopy applications requiring compact, single-mode, narrow linewidth, and tunable laser sources. This approach eliminates contamination issues associated with forming gratings by regrowth in Al-containing structures by using a single growth step and etching the grating after the entire epitaxy is grown. This paper reviews progress in the development of SE-DBR lasers using InGaAs-GaAs-AlGaAs and GaAs-AlGaAs separate confinement heterostructure. Fabrication techniques, design optimization studies, and device performance characteristics are overviewed. Applications of SE-DBRs toward multiwavelength arrays, THz generation via optical heterodyning, and alkali spectroscopy are discussed.

Ultrashort Q-switched pulses from a passively mode-locked distributed Bragg reflector semiconductor laser

A compact semiconductor mode-locked laser (MLL) is presented that demonstrates strong passive Q-switched mode-locking over a wide range of drive conditions. The Q-switched frequency is tunable between 1 and 4 GHz for mode-locked pulses widths around 3.5 ps. The maximum ratio of peak to average power of the pulse-train is >120, greatly exceeding that of similarly sized passively MLLs.

Dual-wavelength distributed Bragg reflector semiconductor laser based on a composite resonant cavity

We report a monolithic integrated dual-wavelength laser diode based on a distributed Bragg reflector (DBR) composite resonant cavity. The device consists of three sections, a DBR grating section, a passive phase section, and an active gain section. The gain section facet is cleaved to work as a laser cavity mirror. The other laser mirror is the DBR grating, which also functions as a wavelength filter and can control the number of wavelengths involved in the laser action. The reflection bandwidth of the DBR grating is fabricated to have an appropriate value to make the device work at the dual-wavelength lasing state. We adopt the quantum well intermixing (QWI) technique to provide low-absorption loss grating and passive phase section in the fabrication process. By tuning the injection currents on the DBR and the gain sections, the device can generate 0.596 nm-spaced dual-wavelength lasing at room temperature.

Mode transitions in distributed Bragg reflector semiconductor lasers: experiments, simulations and analysis

The performance of a multisection distributed Bragg reflector (DBR) semiconductor laser emitting around 1.06 µm is experimentally and theoretically investigated. A thermal-induced change of the refractive index implied by an increase in the injection current yields nearly periodic transitions between neighbouring cavity modes. These transitions are explained by means of a modal analysis and by numerical simulations based on the travelling wave model.

Design of a monolithic tunable laser based on equivalent-chirp grating reflectors

A Vernier-tuned distributed Bragg reflector (DBR) semiconductor laser is an effective monolithic approach for wide wavelength tunability, at the expense, however, of costly electron-beam lithography during fabrication. In this Letter, a tunable laser design with equivalent-chirp based, flat-top envelope grating reflectors is proposed that can be implemented easily by conventional two-beam interference lithography. The principle is described, and a detailed design shows uniform output power (0.08 dB variation) and excellent side-mode suppression ratio (47 dB minimum) within a wide tuning range (>32 nm) through numerical simulation.

Phase Correlation and Linewidth Reduction of 40 GHz Self-Pulsation in Distributed Bragg Reflector Semiconductor Lasers

In this paper, self-pulsation (SP) in a distributed Bragg reflector (DBR) semiconductor laser without a saturable absorber is experimentally and theoretically investigated. Detailed experimental characterizations of the SP DBR laser are reported in the optical and radio-frequency domains. Phase correlation between the longitudinal modes selected by the DBR mirror has been experimentally demonstrated. A theoretical model based on coupled rate equations for three modes has been developed to study the time evolution of phases and amplitudes of the modes. The carrier density modulation, resulting from the beating between adjacent longitudinal modes generates four-wave mixing (FWM) and is responsible for mutual injection locking, leading to passive mode-locking. The calculated power spectral density of the frequency noise derived from the model is in agreement with experimental results and proves that the phases of the longitudinal modes are identically correlated through the FWM process in this type of SP lasers

Wavelength stabilization of a distributed Bragg reflector laser diode by use of complementary current injection.

We have demonstrated wavelength stabilization in an 821-nm AlGaAs three-section tunable distributed Bragg reflector (DBR) semiconductor laser diode (LD) that consists of active, phase-controlled, and DBR regions. We injected two separate, complementary currents into the active and the phase-controlled regions in the DBR-LD to suppress wavelength shift. This modulation method was applied to the LD fundamental wave in a second-harmonic-generation (SHG) laser, and the oscillating wavelength was maintained within the phase-matching acceptance range of the SHG device during modulation. A peak blue-violet light power of 62 mW was obtained for the ideal modulation waveform.

Dispersion-induced power penalties in millimeter-wave signal transmission using multisection DBR semiconductor laser

In this paper, we present a simple analytical model to characterize the effect of fiber chromatic dispersion when using a multisection distributed-Bragg reflector (DBR) semiconductor laser as a millimeter-wave optical transmitter in a millimeter-wave fiber-radio system. We characterize the dispersion penalty of the laser as a function of the laser operating conditions and establish that the penalty is dependent on the distribution of optical power among the modes in the laser output. This, in turn, is dependent on the spectrum-filtering property of the laser DBR section and the gain profile of the laser. In addition to the dispersion penalty, the stability of the generated millimeter-wave carrier from the multisection laser is investigated, including the detected RF power and resulting phase noise. We establish that a compromise must be made when finding the optimum bias condition of the laser which provides minimum dispersion penalty, maximum received RF power, and minimum phase noise of the generated millimeter-wave carrier.

Subharmonic synchronous mode-locking of a monolithic semiconductor laser operating at millimeter-wave frequencies

Optical pulse trains at millimeter-wave frequencies are generated by subharmonic synchronous mode-locking of a monolithic distributed Bragg reflector semiconductor laser, by which an initially passively mode-locked semiconductor laser is stabilized by injecting optical pulses at subharmonic frequencies of its resonant frequency. The stabilized pulse trains are characterized in terms of phase noise, timing jitter, locking range and modulation depth under various injection conditions including injected signal power levels, pulsewidths, and subharmonic numbers. It is also shown that subharmonic synchronous mode-locking can provide pulse trains with a very low level of phase noise (/spl les/-86 dBc/Hz @ 10 kHz offset), reasonably wide locking ranges (4-20 MHz) and low levels of amplitude modulation (96%-99%). Such pulse characteristics are compared with those achieved by the subharmonic hybrid mode-locking scheme, where stabilization is realized by injecting electrical signals at subharmonic frequencies of the laser's resonant frequency. It is shown that subharmonic hybrid mode-locking is only effective at low subharmonic numbers (2-6), while subharmonic synchronous mode-locking can be realized with much larger subharmonic numbers. It is also revealed from the comparison that while subharmonic hybrid mode-locking scheme is simple and cost-effective approach for the generation of high-frequency signals from semiconductor lasers, subharmonic synchronous mode-locking scheme can offer pulse trains using very low-frequency driving electronics with superior performance such as larger locking ranges, and lower levels of phase noise and amplitude modulation.

Wavelength switching using multicavity semiconductorlaser diodes

The authors demonstrate wavelength switching in a novel multicavity distributed Bragg reflector semiconductor laser diode. This new device, which uses an integrated saturable absorber and singlemode fibre Bragg gratings, digitally switches wavelength as a function of drive current between all possible binary combinations.

Frequency-tunable millimetre-wave signal generationusing a monolithic passively mode-locked semiconductor laser

Repetition frequency tuning characteristics of a monolithic passively mode-locked distributed Bragg reflector semiconductor laser are investigated. By injecting current at a passive phase control section, a tuning range of 400 MHz is achieved while keeping the pulse characteristics nearly unchanged. Varying the absorber reverse bias offers an alternative to tune the frequency. By combining these techniques, a total tuning range of 1 GHz is realised.

Tuning characteristics of monolithic passively mode-locked distributed Bragg reflector semiconductor lasers

Tuning characteristics of multicontact passively mode-locked distributed Bragg reflector (DBR) semiconductor lasers are investigated in terms of center wavelengths and pulse repetition frequencies. It is shown that the center wavelength of the pulses can be tuned over a wide range by changing the refractive index of the Bragg reflector section either by means of carrier injection or by thermal effects while maintaining the pulses to be nearly transform-limited. Tuning of the pulse repetition rates is realized by using four different approaches, i.e., current injection to a passive phase-control section, varying of the reverse bias to the absorber, varying of the injection current to the gain region, and thermal effects. Injecting current into the phase-control region results in a tuning range of more than 400 MHz while maintaining the pulses at transform-limited condition. Varying the reverse bias voltage to the absorber is shown to be an alternative to achieve large repetition rate tuning, by which a tuning range of 600 MHz is obtained. By combining these tuning schemes, a total tuning range of more than 1 GHz is realized.

Subharmonic hybrid mode-locking of a monolithic semiconductor laser

Performance of a subharmonically hybrid mode-locked (SH-ML) monolithic semiconductor laser is investigated. A 33-GHz passively mode-locked distributed Bragg reflector semiconductor laser is stabilized by the injection of an electrical signal with a subharmonic frequency of the laser cavity resonance. Systematic measurements on the phase noise, timing jitter, amplitude modulation, and locking bandwidth are performed for the second- and third-order SH-ML conditions, and the results are compared with the fundamental hybrid mode-locking (FH-ML) case. Low timing jitter of less than 0.6 ps, comparable to that under the FH-ML case, is achieved for the both SH-ML cases. The amplitude modulation imposed by the subharmonic driving frequencies is found to be very small (<-24 dBc) for the second-order SH-ML because of the sufficiently low modulation response of the laser at 16.5 GHz. The third-order SH-ML is found to exhibit a very unique locking characteristics, leading to a maximum locking bandwidth of 56 MHz that is even larger than that for the FH-ML case.