Noise In Semiconductor Lasers Research Articles

Optical frequency comb generation using cascaded injection of semiconductor lasers

We study optical frequency comb (OFC) generation using cascaded injection of semiconductor lasers in this work. The OFC generation system is operated in two cascaded optical injection stages. When a master laser optically injects into the first stage with proper injection power and frequency, period-one (P1) dynamics are invoked in an optically injected semiconductor laser of the first stage. Another semiconductor laser in the second stage is then optically injected by the P1 dynamics. With proper injection power adjusted in the second stage, the P1 dynamics are regenerated, and the semiconductor laser relaxation oscillations (ROs) become undamped so that subharmonic oscillations appear. Because a subharmonic oscillation frequency is half of an oscillation frequency of the P1 dynamics, extra optical frequency components appear in the middle of the adjacent optical frequency components of the P1 dynamics, thus signaling OFC generation. The OFC signals exhibit at least 15 comb lines, resulting in a bandwidth greater than 140 GHz. Microwave comb signals are obtained after photodetection, although the microwave linewidth is on the order of a few megahertz because of the semiconductor laser noise. Thus, we propose a cascaded injection-locking scheme to stabilize the P1 dynamics and OFC signals. We have demonstrated pure microwave generations with a linewidth of less than 3 Hz and low phase noise.

3D integration enables ultralow-noise isolator-free lasers in silicon photonics

Photonic integrated circuits are widely used in applications such as telecommunications and data-centre interconnects1–5. However, in optical systems such as microwave synthesizers6, optical gyroscopes7 and atomic clocks8, photonic integrated circuits are still considered inferior solutions despite their advantages in size, weight, power consumption and cost. Such high-precision and highly coherent applications favour ultralow-noise laser sources to be integrated with other photonic components in a compact and robustly aligned format—that is, on a single chip—for photonic integrated circuits to replace bulk optics and fibres. There are two major issues preventing the realization of such envisioned photonic integrated circuits: the high phase noise of semiconductor lasers and the difficulty of integrating optical isolators directly on-chip. Here we challenge this convention by leveraging three-dimensional integration that results in ultralow-noise lasers with isolator-free operation for silicon photonics. Through multiple monolithic and heterogeneous processing sequences, direct on-chip integration of III–V gain medium and ultralow-loss silicon nitride waveguides with optical loss around 0.5 decibels per metre are demonstrated. Consequently, the demonstrated photonic integrated circuit enters a regime that gives rise to ultralow-noise lasers and microwave synthesizers without the need for optical isolators, owing to the ultrahigh-quality-factor cavity. Such photonic integrated circuits also offer superior scalability for complex functionalities and volume production, as well as improved stability and reliability over time. The three-dimensional integration on ultralow-loss photonic integrated circuits thus marks a critical step towards complex systems and networks on silicon.

Numerical analysis on the impact of optical feedback and nonlinear gain on the dynamics and intensity noise of semiconductor laser

Numerical analysis on the impact of optical feedback and nonlinear gain on the dynamics and intensity noise of semiconductor laser

Principles, Measurements and Suppressions of Semiconductor Laser Noise—A Review

Semiconductor lasers are widely used in incoherent/coherent optical communications, optical fiber sensing, and lidar due to their small size, high efficiency, and immunity to vibrations. To support the continuous evolution of these high-performance application systems, the noise characteristics of semiconductor lasers play a key role and the noise levels need to be reduced to unprecedentedly low values (such as quantum limit). In this paper, a comprehensive overview on the principles, measurements, and suppressions of semiconductor laser noises are provided. First, we introduce the analysis models and key performance indicators of semiconductor lasers related to noise. Then, different noise measurement systems are investigated for semiconductor lasers and the noise characteristics are fully analyzed. Next, the noise suppression methods towards semiconductor lasers are demonstrated from three aspects: the chip structures, the external cavity optical feedback technology and the driving and controlling circuits. Finally, we summarize the recent advances on the noise measurement and suppression of semiconductor laser, future prospects are also discussed.

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

Intensity Noise of Semiconductor Lasers Induced by Inter-Mode Beating

Beating between the lasing main mode and the non-lasing side modes is one of the intensity noise sources of single longitudinal mode lasers. Its characteristics were investigated experimentally recent years. This paper presents a theoretical study of mode-beating noises in semiconductor lasers, and intends to explain the experimentally observed phenomena. The effects of coherent population oscillation (CPO) induced by mode beating on gain coefficient and on reflective index are analyzed based on Maxwell-Bloch equation and rate equations. The power ratio of the side mode over its conjugation mode generated by four wave mixing (FWM) is discussed; formulas of amplitude and frequency of mode beating intensity noise are given with relations to pump levels and mode orders. The obtained results are suitable for the edge emitting diode lasers and the external cavity lasers. The line shape of mode beating intensity noises is discussed based on CPO-induced phase noise, giving explanations of the experimentally observed phenomenon of multiple sub-peak spectra. The roles of intensity noise reduction by nonlinear optical absorber (NLA) inserted in the laser cavity are described. More factors related to the mode beating noise are discussed qualitatively, such as spectral hole burning of gain (SHB), the effect of external cavity, and higher order FWM.

Optimum parameters controlling distortion and noise of semiconductor laser under analog multichannel modulation

This paper presents a comprehensive modelling and simulation study on the optimum parameters that control the distortion and noise of semiconductor lasers (SLs) subject to multichannel modulation for use in analog cable television (CATV) fibre links. The study is based on numerical integration of the rate equation model of the semiconductor laser. The parameters comprise the modulation index per channel (m / ch), number of loaded channels (N) and fibre length $$(L_{F})$$ . The signal distortions include the composite second-order (CSO) and composite triple beat (CTB) distortions. The noise is assessed in terms of the relative intensity noise (RIN) and carrier-to-noise ratio (CNR). In order to achieve acceptable CNR values for SL, m / ch should be less than 7.5 and 2% when loading 12 and 80 channels, respectively. For the CATV fibre link with $$L_{F} = 10 \hbox { km}$$ , the increase in the number of channels from 12 to 80 corresponds to lowering the optimum value of m / ch from 7 to 1%. The increase of $$L_{F}$$ to 50 km limits the optimum value of m / ch between 1.4 and 1%, which corresponds to loading between 12 and 17 channels only.

Stochastic Differential Equation Model for Spontaneous Emission and Carrier Noise in Semiconductor Lasers

We present a new stochastic differential equation model for the spontaneous emission noise and carrier noise in semiconductor lasers. The correlations between these two types of noise have often been neglected in recent studies of the effects of the noise on the laser dynamics. However, the classic results of Henry show that the intensity noise and the carrier noise are strongly negatively correlated. Our model demonstrates how to properly account for these correlations since the corresponding diffusion coefficients agree exactly with those derived by Henry. We show that in fact in the correct model the spontaneous emission noise and the carrier noise are driven by the same Wiener processes. Furthermore, we demonstrate that the nonzero correlation time of the physical noise affects the mean dynamics of both the electric field amplitude and the carrier number. We show that these are systematic corrections that can be described by additional drift terms in the model.

Integrated Pound\u2212Drever\u2212Hall laser stabilization system in silicon

Low noise stable lasers have far-reaching applications in spectroscopy, communication, metrology and basic science. The Pound−Drever−Hall laser stabilization technique is widely used to stabilize different types of lasers in these areas. Here we report the demonstration of an integrated Pound−Drever−Hall system that can stabilize a low-cost laser to realize a compact inexpensive light source, which can ultimately impact many fields of science and engineering. We present an integrated architecture utilizing an electronically reconfigurable Mach−Zehnder interferometer as the frequency reference to reduce the frequency noise of semiconductor lasers by more than 25 dB and the relative Allan deviation by more than 12 times at 200 μs averaging time. Compared to the bench-top implementations, the integrated Pound−Drever−Hall system has significantly lower power consumption, less sensitivity to the environmental fluctuations and occupies an area of only 2.38 mm2. The photonic and electronic devices are integrated on a standard 180 nm complementary metal-oxide semiconductor silicon-on-insulator process.

Modeling of relative intensity noise and terminal electrical noise of semiconductor lasers using artificial neural network

In this paper, artificial neural network (ANN) is used to predict the source laser’s relative intensity noise (RIN) and the terminal electrical noise (TEN) of semiconductor lasers. For this purpose, the multi-layer perceptron (MLP) neural network trained with the back propagation algorithm is used. To develop this model, the normalized bias current and frequency are selected as the input parameters and the RIN and TEN of semiconductor lasers are selected as the output parameters. The obtained results show that the proposed ANN model is in a good agreement with the numerical method, and a small error between the predicted values and the numerical solution is obtained. Therefore, the proposed ANN model is a useful, reliable, fast and cheap tool to predict the RIN and TEN of semiconductor lasers.

Harmonic and intermodulation distortions and noise associated with two-tone modulation of high-speed semiconductor lasers

We present results of modeling and simulation of the harmonic and intermodulation distortions as well as the intensity noise of high-speed semiconductor lasers under two-tone modulation. Multiple quantum-well lasers are considered, which are characterized by large differential gain and a modulation bandwidth of about 25GHz. The study is based on the rate equation model of semiconductor lasers excited by injection current with two sinusoidal tones separated by a radio frequency. The modulated laser signal is modeled in both the time and frequency domains. The time domain characteristics include the fluctuating waveform, while the frequency domain characteristics include the frequency spectrum of the relative intensity noise (RIN), carrier-to-noise ratio, modulation response, harmonic distortion, and the second- and third-order intermodulation distortions (IMD2 and IMD3). The analysis is performed for three frequencies of 5, 15, and 24 GHz, which are, respectively, lower, comparable, and higher than the laser relaxation frequency. The range of the modulation depth covers the regimes of small and large-signal modulation. We show that both RIN and IMD3 of two-modulated laser are minimum when the modulation frequency is 5GHz, and maximum when the modulation frequency is 24 GHz. The second-order harmonic distortion, IMD2, and IMD3 values are larger in the vicinity of relaxation oscillations and increase with the modulation index, especially under large-signal modulation.

Modeling and simulation of dynamics and noise of semiconductor lasers under NTSC modulation for use in the CATV technology

We investigate the dynamics and noise of semiconductor lasers (SLs) subject to analog modulation with the frequency plan of the National Television Standards Committee (NTSC) for use in the community access television (CATV) systems. The investigations are done in both the time and frequency domains as important methodologies to upgrade the optical CATV systems. The study is based on the rate equation model of the laser. The modulation dynamics is classified into four distinct types according to the waveform of the modulated signal, and the frequency spectra of the relative intensity noise (RIN) of these types are characterized. We show that the laser emits continuous and regular period signals under weak modulation. When the modulation index exceeds 43%, i.e. the modulation current exceeds the bias level above threshold, the laser emits clipped signals superposed by relaxation oscillation. The increase in the modulation index by about 50% in channels beyond channel #24 makes the laser emitting clipped pulsed signals superposed by relaxation oscillation. The laser attains higher noise levels (∼−108 dB/Hz) when it emits pulses, whereas the noise is lowest (∼−170 dB/Hz) when the signal is continuous.

Mode-competition noise associated with microwave modulation of multimode semiconductor lasers

We analyze the mode-competition (MC) phenomenon and the associated noise in multimode semiconductor lasers at microwave modulation. The study is based on the multimode rate-equation model, which takes into account the mechanisms of modal gain suppression. The MC is evaluated by the correlation coefficients between oscillating modes in the laser cavity. We show that an increase in the modulation depth changes the mode coupling from anticorrelation to positive correlation and then to complete coupling, which corresponds to emission of periodic pulses. The frequency spectra of relative intensity noise (RIN) exhibit sharp peaks at the modulation frequency and higher harmonics. The increase in the modulation depth is associated with suppression of the total and modal RIN under high-frequency modulation and with noise enhancement under low-frequency modulation.

Study of the optical feedback-induced noise in semiconductor lasers and applications to the optic disc system

The dynamics and noise of semiconductor lasers under optical feedback (OFB) have been simulated. The study is performed as applied to an optic-disc system in which laser radiation is reflected by the disc surface and re-injected into the laser cavity. We examine the possibility of suppressing OFB- induced noise in the optic-disc system by the technique of superposition of high-frequency current. The study is based on numerical integration of the time-delay rate equations of semiconductor lasers under OFB. The laser noise is evaluated in terms of the spectral profile of relative intensity noise (RIN). It is shown that RIN is enhanced when states of chaos are generated, and attains minimum levels under continuous- wave operation just before the laser starts the route to chaos. The suppression of RIN in the low-frequency regime is achieved when the superposition-current frequency exceeds the laser resonance frequency by factors of 0.8, 1.0, and 1.1 and when the modulation depth exceeds 0.4. DOI: 10.3103/S1541308X14010129

Theoretical Modeling of Intensity Noise in InGaN Semiconductor Lasers

This paper introduces modeling and simulation of the noise properties of the blue-violet InGaN laser diodes. The noise is described in terms of the spectral properties of the relative intensity noise (RIN). We examine the validity of the present noise modeling by comparing the simulated results with the experimental measurements available in literature. We also compare the obtained noise results with those of AlGaAs lasers. Also, we examine the influence of gain suppression on the quantum RIN. In addition, we examine the changes in the RIN level when describing the gain suppression by the case of inhomogeneous spectral broadening. The results show that RIN of the InGaN laser is nearly 9 dB higher than that of the AlGaAs laser.

The frequency noise and spectral linewidth in semiconductor ring lasers

Numerical analyses for power spectral density of frequency noise (FN) and spectral linewidth in monolithic semiconductor ring laser (SRL) operating in the bistable unidirectional regime are performed in this paper. The Langevin noise sources for electric field and carrier density fluctuations are also taken into account in the frequency-domain theoretical model. The influences of several important physical parameters on the FN properties and laser linewidth are clearly demonstrated, including the injection current, linewidth enhancement factor and the particular backscattering coefficient. Due to the particular backscattering in SRLs, the calculated linewidths are relatively higher than that from the conventional Henry formula. The laser linewidth shows an exponential relationship with the backscattering strength.

Chaos and noise control by current modulation in semiconductor lasers subject to optical feedback

This paper introduces comprehensive large-signal analyses of modulation dynamics and noise of a chaotic semiconductor laser. The chaos is induced by operating the laser under optical feedback (OFB). Control of the chaotic dynamics and possibility of suppressing the associated noise by sinusoidal modulation are investigated. The studies are based on numerical solutions of a time-delay rate equation model. The deterministic modulation dynamics of the laser are classified into seven regular and irregular dynamic types. Variations of chaotic dynamics and noise with sinusoidal modulation are examined in both time and frequency domains over wide ranges of the modulation depth and frequency. The results showed that chaotic dynamics can be converted into five distinct dynamic types; namely, continuous periodic signal (CPS), continuous periodic signal with relaxation oscillations (CPSRO), periodic pulse (PP), periodic pulse with relaxation oscillations (PPRO) and periodic pulse with period doubling (PPPD). The relative intensity noise (RIN) of these types is characterized when the modulation frequencies are much lower, comparable to, and higher than the resonance frequency. Suppression of RIN to a level 8 dB/Hz higher than the quantum limit was predicted under the CPS type when the modulation frequency is 0.9 times the resonance frequency and the modulation depth is 0.14.

Reduction of Intensity Noise in Semiconductor Lasers by Simultaneous Usage of the Superposition of High Frequency Current and the Electric Negative Feedback

Reduction of the intensity noise in semiconductor lasers is an important subject for the higher performance of an application. Simultaneous usage of the superposition of high frequency current and the electric negative feedback loop was proposed to suppress the noise for the higher power operation of semiconductor lasers. Effective noise reduction of more than 25 dB with 80 mW operation was experimentally demonstrated. key words: semiconductor laser, optical feedback noise, noise reduction, electric negative feedback, high frequency current superposition

Estimation of frequency noise in semiconductor lasers due to mechanical thermal noise

We evaluate mechanical thermal noise in semiconductor lasers, applying a methodology developed for fixed-spacer cavities for laser frequency stabilization. Our simple model determines an underlying fundamental limit for the frequency noise of free-running semiconductor laser, and provides a framework where the noise may be potentially reduced with improved design.

Dynamics and noise of fiber-grating semiconductor lasers affected by the line-width enhancement factor

This paper numerically investigates the effect of the line-width enhancement factor on the dynamics and the intensity noise of InGaAs/InP lasers pumping in the wavelength of 980 nm at the strong optical feedback limit. The investigation is performed based on an improved time-delay rate equation model of a single-mode laser. The analyses are performed in terms of the temporal trajectory of the laser intensity, bifurcation diagram, relative intensity noise and injection current. The simulation results indicate that the laser, under strong optical feedback, mainly operates in CW, pulsation or chaos operation depending on the line-width enhancement factor and injection current values. At larger values of the line-width enhancement factor and injection current the pulsing operation becomes more dominant over wider range of strong optical feedback. The corresponding relative intensity noise level is close to or slightly larger than the level of the solitary laser noise. The optical feedback noise is found to be as low as the quantum noise level when the laser is operated in pulsing region and at larger values of the line-width enhancement factor and injection current.