Linewidth Of Semiconductor Lasers Research Articles

Narrow linewidth laser based on a sidewall grating active distributed Bragg reflector.

We demonstrated a narrow linewidth semiconductor laser based on a deep-etched sidewall grating active distributed Bragg reflector (SG-ADBR). The coupling coefficients and reflectance were numerically simulated for deep-etched fifth-order SG-ADBR, and a reflectance of 0.86 with a bandwidth of 1.04 nm was obtained by the finite element method for a 500-period SG-ADBR. Then the fifth-order SG-ADBR lasers were fabricated using projection i-line lithography processes. Single-mode lasing at 1537.9 nm was obtained with a high side-mode suppression ratio (SMSR) of 65 dB, and a continuous tuning range of 10.3 nm was verified with SMSRs greater than 53 dB. Furthermore, the frequency noise power spectral density was characterized, from which a Lorentzian linewidth of 288 kHz was obtained.

Monolithically Integrated Extended Cavity Diode Laser with 32 kHz 3 dB Linewidth Emitting at 1064 nm

AbstractThe spectral linewidth of semiconductor lasers is a crucial performance parameter in a growing number of applications. A common method to improve the coherence of the laser relies on increasing the optical cavity length by an extended section without gain material. Here, this extended cavity diode laser (ECDL) concept is realized in a monolithic device at 1064 nm wavelength. This is accomplished by applying a two‐step epitaxy in the aluminum gallium arsenide material system to selectively remove the active layers in a specific section of the chip. The extended passive section decreases the 3 dB linewidth to 32 kHz at 1 ms integration time. A direct comparison between the performance of the monolithic ECDL and a distributed Bragg reflector laser from the same wafer demonstrates the feasibility of the approach. The results in terms of frequency noise, side mode suppression ratio, injection current threshold, and slope efficiency show that the passive section reduces the laser linewidth while the additional interfaces within the laser cavity created by the manufacturing process do not deteriorate the electro‐optical properties or frequency stability. This opens the possibility for the realization of gallium arsenide based photonic integrated circuits by monolithically combining active and low‐loss passive waveguides.

Narrow linewidth semiconductor laser with a multi-period-delayed feedback photonic circuit.

A multi-period-delayed feedback (MPDF) photonic circuit constructed by a Sagnac ring and two coupled rings was designed. By coupling a distributed feedback (DFB) laser diode (LD) with the MPDF, a narrow linewidth semiconductor laser was demonstrated. The linewidth of the DFB-LD with MPDF was narrowed to be around 2 kHz, which is reduced by three orders of magnitude, and the linewidth reduction capability could be maintained when the wavelength of the DFB-LD was tuned in a range wider than 3 nm. The laser frequency stability can also be improved using the proposed technique, and the frequency fluctuation was reduced for nearly 8 times in comparison with the DFB-LD.

Narrow Linewidth Semiconductor Laser Based on Anti-Symmetric Bragg Grating

We present a new configuration of narrow linewidth semiconductor lasers (NLSLs) based on a novel narrow-band reflector (NBR) with π phase-shifted anti-symmetric Bragg grating (π-ASBG). Based on this configuration, two specific laser structures are theoretically analyzed. The effective length of Bragg grating is highly increased due to the double hybrid-mode resonances between the fundamental transverse electric (TE0) mode and first-order transverse electric (TE1) mode in the π-ASBG with the aid of a uniform grating reflector. The narrowest linewidth of ∼2.4 kHz is obtained of the proposed NLSLs, which is much lower than the traditional NLSLs with external uniform Bragg grating in the case of the same grating length.

Modelling of intensity noise, frequency noise and linewidth of semiconductor laser and their dependence on optical gain formulation

Modelling of intensity noise, frequency noise and linewidth of semiconductor laser and their dependence on optical gain formulation

Research progress of high power semiconductor laser pump source

High power semiconductor lasers are the main pump source for solid-state lasers and fiber lasers. The improvement in the performance of laser pump sources directly promotes the development of solid-state lasers, fiber lasers and other lasers. The article introduces the latest research progress of 8xx nm and 9xx nm semiconductor laser pump sources. The output power research level of 8xx nm single-emitter laser has reached 18.8 W@95 µm, the output power research level of 8xx nm laser bar has reached 1.8 kW(QCW), the output power research level of 9xx nm single-emitter laser has reached 35 W@100 µm, the output power research level of 9xx nm laser bar has reached 1.98 kW(QCW). The output power of a narrow linewidth semiconductor laser with a linewidth ＜1 nm can reach 14 W. The development trend of semiconductor laser pump source in the future is forecasted.

Waveguide external cavity narrow linewidth semiconductor lasers

Narrow linewidth light source is a prerequisite for high-performance coherent optical communication and sensing. Waveguide-based external cavity narrow linewidth semiconductor lasers (WEC-NLSLs) have become a competitive and attractive candidate for many coherent applications due to their small size, volume, low energy consumption, low cost and the ability to integrate with other optical components. In this paper, we present an overview of WEC-NLSLs from their required technologies to the state-of-the-art progress. Moreover, we highlight the common problems occurring to current WEC-NLSLs and show the possible approaches to resolving the issues. Finally, we present the possible development directions for the next phase and hope this review will be beneficial to the advancements of WEC-NLSLs.

Quantum analysis of a traveling-wave electro-optic phase modulator in the presence of the phase noise from a radio frequency oscillator and a laser

Quantum analysis has been done for the traveling-wave (TW) electro-optic phase modulator in the presence of the phase noise of a radio frequency (RF) oscillator and a laser source, in which the Hamiltonian for an active section of the phase modulator system is derived. The effect of RF phase noise from the oscillator and a phase velocity mismatch (PVM) between optical photons and the RF field are included in the Hamiltonian. The time evolution of the field operator of the laser in the TW electro-optic phase modulator is derived by the Heisenberg equation of motion. The action of a TW electro-optic phase modulator in the presence of the two distinct weak noises—classical phase noise because of RF and quantum phase noise caused by a laser—has been evaluated and explained in terms of the second-order temporal correlation function and power spectrum. The power spectrum has been written as a function of the semiconductor laser linewidth, an enhancement factor in the laser linewidth, and the RF oscillator linewidth. The results are applied to analyze the basic model of a frequency-coded quantum key distribution (FC-QKD) system. The quantum bit error rate (QBER), the first-order optical intensity correlation function, and the spectrum of intensity fluctuation have been calculated for the partially coherent regime to evaluate the performance of the FC-QKD system.

On-chip optical narrowband reflector based on anti-symmetric Bragg grating.

We propose an on-chip optical narrowband reflector (NBR) based on two cascaded Bragg gratings (BGs). A π phase shifted anti-symmetric Bragg grating (π-PS-ASBG) and a rear uniform Bragg grating (UBG), are in-line connected. The π-PS-ASBG provides a hybrid mode resonance between the even- and odd TE (TE0 and TE1) modes, while the UBG is used as a rear reflector to reflect the TE0 mode that transmitted from the π-PS-ASBG. Different from traditional UBG, the reflection bandwidth decreases when the coupling coefficient increases. The calculated 3-dB bandwidth is 0.16 nm when the whole grating length is 400 µm. The proposed NBR can be applied in the cases requiring narrow reflection such as narrow linewidth semiconductor lasers.

Narrow linewidth DBR laser based on high order Bragg grating defined by i-line lithography

In order to obtain narrow linewidth semiconductor laser around 1564 nm, we design a distributed Bragg reflector (DBR) laser with high-order Bragg gratings (HOBGs) using butterfly encapsulation. The DBR laser is fabricated only by i-line lithography technology with grating period of 4. 84μm, groove width of 1. 5μm and grating length of 72μm on a strip width of 4μm. The 1mm-long devices achieved an output power of 9.9 mW and a side mode suppression ratio (SMSR) more than 30 dB without facet coating at an injection current of 80 mA. The lasers showed ultra-narrow Lorentz linewidth of 70 kHz. This paper provides a simple method for large-scale production of narrow linewidth semiconductor lasers.

Linewidth Narrowing of Mutually Injection Locked Semiconductor Lasers with Short and Long Delay

A simple and effective approach to semiconductor laser linewidth narrowing via mutual injection locking is proposed and demonstrated in both short and long delay regimes. A theoretical analysis is presented to investigate the linewidth behavior of semiconductor lasers under mutual injection locking. Experimental demonstrations in short and long delay regimes are implemented by integrated devices and a fiber link system, respectively. Locking condition and dependence of laser linewidth on coupling parameters in both regimes are studied, confirming mutual injection locking as a practical method for linewidth narrowing. For the short-delayed integrated lasers, a linewidth narrowing factor of 13 is demonstrated and sub-MHz linewidth is achieved, while for the long-delayed lasers coupled by fiber link, the intrinsic linewidth is reduced to sub-100 Hz.

Thermal design and optimization of narrow linewidth semiconductor lasers

Thermal design and optimization of narrow linewidth semiconductor lasers

A newly designed high-spectral-resolution Rayleigh temperature lidar based on two-stage Fabry–Perot interferometer

A two-stage Fabry–Perot interferometer (FPI)-based high-spectral-resolution (HSR) Rayleigh temperature lidar technology is proposed that is capable of simultaneously detecting tropospheric temperature and aerosol optical properties with high-precision. The system structure is designed and the measurement principle is analysed. A two-channel integrated FPI used forming a two-stage FPI ensures the relative stability of the two FPI spectrums. The first-stage FPI with high spectral resolution can effectively separate Mie and Rayleigh signals to derive the signal components. Two adjacent-order transmission spectrums of the second-stage FPI are just located in the two wings of Rayleigh–Brillouin (R–B) scattering spectrum to measure temperature. Two multimode polarization insensitive optical circulators used in receiver system can achieve high-efficiency utilization of signals. A narrow linewidth semiconductor laser at 852 nm is used as light source. Using the selected and optimized system parameters, the lidar performance simulation results show that in the sunny weather conditions for 0.15WSr–1 m–2 nm–1 sky brightness, with 0.3 W laser power, a 30 cm diameter telescope, 60 m range resolution and 30 min observation time, the temperature measurement errors are below 0.4 K in night-time and below 1.6 K in daytime; the relative measurement errors of backscatter ratio are below 0.04% in night-time and below 0.13% in daytime respectively up to 6 km height. Compared with the traditional FPI-based HSR technique, the technique we proposed can improve the detection accuracy of temperature by 2.5 times and can also significantly improve the detection accuracy of backscatter ratio.

Integrated Semiconductor Laser Optical Phase Lock Loops

An Optical Phase Lock Loop (OPLL) is a feedback control system that allows the phase stabilization of a laser to a reference laser with absolute but adjustable frequency offset. Such phase and frequency locked optical oscillators are of great interest for sensing, spectroscopy, and optical communication applications, where coherent detection offers advantages of higher sensitivity and spectral efficiency than can be achieved with direct detection. As explained in this paper, the fundamental difficulty in realising an OPLL is related to the limitations on loop bandwidth and propagation delay as a function of laser linewidth. In particular, the relatively wide linewidth of semiconductor lasers requires short delay, which can only be achieved through shortening of the feedback path, which is greatly facilitated through photonic integration. This paper reviews the advances in the development of semiconductor laser-based OPLLs and describes how improvements in performance have been enabled by improvements in photonic integration technology. We also describe the first OPLL created using foundry fabricated photonic integrated circuits and off-the-shelf electronic components. Stable locking has been achieved for offset frequencies between 4 and 12 GHz with a heterodyne phase noise below –100 dBc/Hz at 10 kHz offset. This is the highest performance yet reported for a monolithically integrated OPLL and demonstrates the attractiveness of the foundry fabrication approach.

Theorical analysis of a monolithic all-active three-section semiconductor laser

We propose a novel semiconductor laser structure. It is composed of three cascaded active sections: a Fabry-Pérot laser section sandwiched between two gain-coupled distributed feedback (DFB) laser sections. We have modeled this multi-section structure. The simulation results show that compared with index- and gain-coupled DFB lasers, a significant reduction in the longitudinal spatial-hole burning can be obtained with the proposed device, and that this leads to a stable single longitudinal mode operation at relatively high optical power with a SMSR exceeding 56dB. Full Text: PDF ReferencesL.A. Coldren, "Monolithic tunable diode lasers", IEEE J. Select. Topics Quant. Electron. 6, 988 (2000) CrossRef O. Kjebon, R. Schatz, S. Lourdudoss, S. Nilsson, B. Stalnacke, L. Backbom, "30 GHz direct modulation bandwidth in detuned loaded InGaAsP DBR lasers at 1.55 [micro sign]m wavelength", Electron. Lett. 33(6), 488 (1997). CrossRef N. Kim, J. Shin, E. Sim, C.W. Lee, D.-S. Yee, M.Y. Jeon, Y. Jang, K.H. Park, "Monolithic dual-mode distributed feedback semiconductor laser for tunable continuous-wave terahertz generation", Opt. Expr. 17(16), 13851 (2009). CrossRef M.J. Wallace, R. ORreilly Meehan, R.R Enright, F. Bello, D. Mccloskey, B. Barabadi, E.N. Wang, J.F. Donegan, "Athermal operation of multi-section slotted tunable lasers", Opt. Expr. 25(13), 14426 (2017). CrossRef J.E. Carroll, J.E.A. Whiteaway, R.G.S. Plumb, "Distributed Feedback Semiconductor Lasers", Distributed feedback semiconductor lasers (IEE and SPIE, 1998). CrossRef H. Ghafour-Shiraz, Distributed Feedback Laser Diodes and Optical Tunable Filters (Wiley, 2003). CrossRef D.D. Marcenac, Ph.D dissertation (University of Cambridge, 1993). DirectLink L.M. Zhang, J.E. Carroll, C. Tsang, "Dynamic response of the gain-coupled DFB laser", IEEE J. Quant. Electr. 29, 1722 (1993). CrossRef W. Li, W.-P. Huang, X. Li, J. Hong, "Multiwavelength gain-coupled DFB laser cascade: design modeling and simulation", IEEE J. Quant. Electro. 36(10), 1110 (2000). CrossRef B.M. Mehdi, H. Rachid, in Proc. 3rd Intern. Conf. on Embedded Systems in Telecomm. and Instrument., Annaba, Algeria (2016). DirectLinkC. Henry, "Theory of the linewidth of semiconductor lasers", IEEE J.Quant. Electr. QE-18, 259 (1982). CrossRef K. Takaki, T. Kise, K. Maruyama, N. Yamanaka, M. Funabashi, A. Kasukawa, "Reduced linewidth re-broadening by suppressing longitudinal spatial hole burning in high-power 1.55-/spl mu/m continuous-wave distributed-feedback (CW-DFB) laser diodes", IEEE J. Quant. Electr. 39, 1060 (2003) CrossRef

Semiconductor laser linewidth reduction by six orders of magnitude via delayed optical feedback.

We demonstrate a coherence increase by six orders of magnitude of a standard quantum well semiconductor laser. Using a simple, optical-fiber-based feedback scheme, we stabilize the laser in a high-gain mode of a long external cavity. In a modified self-heterodyne measurement, we mix the high-gain mode with a strongly suppressed side mode and obtain an interference linewidth of only 12.6Hz, corresponding to a decoherence of (3.1±2.9)Hz. In an independent characterization using an etalon, we deduce an upper limit of 300Hz for the laser linewidth. The laser stably resides in this mode for tens of seconds. Our results agree with theoretical predictions.

A recirculating delayed self-heterodyne method using a Mach–Zehnder modulator for kHz-linewidth measurement

Abstract A laser linewidth measurement method which uses a Mach–Zehnder electro-optic modulator (MZM) is proposed in a loss-compensated recirculating delayed self-heterodyne interferometer (LC-RDSHI). Compared with the traditional acousto-optic modulator (AOM), the electro-optic modulator has the merits of broader bandwidth, lower insertion loss, higher extinction ratio and thus, a wider application. A theoretical analysis shows that the power spectrum curve of the novel measurement system is a Lorentzian line, which fits well with experiment. The linewidth is measured to be 137 ± 7 kHz at a frequency shift of 4 GHz. Measurement of a distributed feedback Bragg (DFB) laser has manifested that the linewidth broadens from 98.5 kHz to 137.4 kHz as the operating temperature changes by 16 °C. This work will allow investigation of narrow linewidth semiconductor and fiber laser stability.

Semiconductor laser linewidth

The contribution of quantum fluctuations of the electromagnetic-field amplitude and phase and the medium to the semiconductor laser linewidth is found. It is shown that this contribution increases the linewidth by an order of magnitude in comparison with the contribution of spontaneous radiation.

Optical Negative Feedback for Linewidth Reduction of Semiconductor Lasers

We propose a coherent optical negative feedback method for reducing linewidth of single-mode semiconductor lasers, which requires only an optical filter. Results of numerical analysis indicate that the power spectral density of FM noise can be reduced by more than 40 dB and the subkilohertz spectral linewidth can be obtained with our method when the spectral linewidth is 10 MHz under a free running condition. From a proof-of-concept experiment, we confirmed that the spectral linewidth of a single-mode semiconductor laser is reduced when using our method from 6.4 MHz to 6.5 kHz. This result confirms that the spectral linewidth can be reduced by at least 30 dB, which proves the validity of our method.

High-Q microsphere resonators for angular velocity sensing in gyroscopes

A resonator gyroscope based on the Sagnac effect is proposed using a core unit that is generated by water-hydrogen flame melting. The relationship between the quality factor Q and diameter D is revealed. The Q factor of the spectral lines of the microsphere cavity coupling system, which uses tapered fibers, is found to be 106 or more before packaging with a low refractive curable ultraviolet polymer, although it drops to approximately 105 after packaging. In addition, a rotating test platform is built, and the transmission spectrum and discriminator curves of a microsphere cavity with Q of 3.22×106 are measured using a semiconductor laser (linewidth less than 1 kHz) and a real-time proportional-integral circuit tracking and feedback technique. Equations fitting the relation between the voltage and angular rotation rate are obtained. According to the experimentally measured parameters, the sensitivity of the microsphere-coupled system can reach 0.095∘/s.