Optically-pumped semiconductor squeezed-light generation

The theory presented shows that light emitted by low-temperature semiconductors under intense optical pumping (with fluctuations at the shot-noise level, SNL) should be amplitude-squeezed down to half the SNL at nonzeri frequencies. Amplitude squeezing may also be obtained at zero frequency when spontaneous carrier recombination is significant. It is essential that the optical gain depends on photon emission rate, e.g. as a result of spectral-hole burning. A commuting-number theory that agrees exactly with quantum theory for large particle numbers is employed. Comparison is made with results previously reported for three-level atom lasers.     

High-frequency optical signal generation in a semiconductor laser by incoherent optical feedback

This work examines the feasibility of using incoherent optical feedback to generate high-frequency optical signals in a semiconductor laser. At a roundtrip feedback distance of 30 cm, a signal appears at around 1 GHz while the laser output is kept in single longitudinal mode and single polarization. The proposed method does not use any external modulation or saturable absorber. Some of the signal's properties are discussed as well.     

Design of waveguide-integrated semiconductor laser sources for optical frequency comb generation

A numerical study of threshold gain and modal dispersion in integrated semiconductor laser optical frequency comb sources is presented. We consider an example device where one of the cleaved facets of the laser is replaced by a short Bragg grating section and show that as many as 16 modes can be selected at the first harmonic of the underlying Fabry-Perot cavity. An intracavity approach to limiting the grating-induced dispersion that can be implemented directly through the grating profile is demonstrated.     

Chaos generation in a semiconductor ring laser with an optical injection

Two chaos generation schemes are demonstrated numerically based on a semiconductor ring laser (SRL) with either a constant or a chaotic optical injection from an external distributed feedback (DFB) laser. Under a certain bias current, the chaotic output can be generated by the SRL with appropriate injection parameters. Parameter map is achieved numerically to show types of oscillation in the SRL. Bifurcation diagrams and Lyapunov exponent spectra roughly describe the routes to chaos for the SRL with disturbance. A bandwidth-enhanced chaos generation can be describes based on the chaotic optical injection scheme. The bandwidth of the bandwidth-enhanced chaos generated is about 12 GHz, which achieves approximately a two-fold increase compared with the constant injection scheme.     

Wavelength-tunable optical pulse generation from a fiber ring laser with a reflective semiconductor optical amplifier

This work describes, for the first time, wavelength-tunable optical pulse generation from a fiber ring laser with a reflective semiconductor optical amplifier. The optical signal to noise ratio of this fiber laser is higher than 49 dB over the wavelength-tunable range of 16 nm. Performance of this fiber ring laser operated at different wavelengths is also discussed.     

Classical theory of laser noise

The classical theory of laser noise treats light in a classical manner, yet agrees with quantum theory for large particle numbers. The basic concept is that laser noise is caused by atomic jumps between lower and upper levels, and that atoms subjected to classically-prescribed optical fields are independent. The treatment of amplitude noise of single-mode cavities containing resonant three-level atoms is applicable to semiconductor lasers at moderate power. At high power one must account for the dependence of the gain on optical power and for state-occupancy fluctuations. The phasor theory that attributes noise to the beat between the oscillating field and the field spontaneously emitted in the mode by excited-state atoms cannot be understood consistently in semiclassical terms.     

Classical theory of laser linewidth

The classical theory of light fluctuations rests on the intuitive concept that jumps between atomic states occur at independent times when the optical field has a prescribed value. The statistical properties of phase-noise sources are obtained in the present paper by applying this principle to detuned atoms. Formulae for amplitude and phase fluctuations coincide with quantum-theory results even when non-classical states of light are generated. Theories employing semiclassical or quantum concepts are reviewed. We consider particularly the linewidth of laser oscillators operating below and above threshold when the atomic polarization cannot be adiabatically eliminated. Quantum-theory results by Lax (1966) are recovered from classical theory in a straightforward manner. More general results are given for dispersive loads, applicable to external-cavity lasers and relevant to gain guidance. It is emphasized that the K-factor as calculated by Petermann is applicable only below threshold. When more than one emitting element is present, population rate equations need to be considered and the linewidth decreases when the pump fluctuations are suppressed. The role of gain compression relating to semiconductor lasers is discussed. It is shown that at low and moderate powers gain compression reduces the effective phase-amplitude coupling factor, . But at high power a number of mechanisms contribute to linewidth rebroadening. One of them is the statistical (quasi-thermal equilibrium) fluctuation of the refractive index. General concepts applicable to broadband light are outlined in an appendix.     

Quasi-phase-matched generation of optical intensity waves

The evolution of modulated light in a nonlinear medium, when described in terms of intensity waves, depends critically on a phase-matching condition for the intensity waves. We formally develop the conditions for quasi-phase matching of the interacting intensity waves and show that a periodic nonlinearity can be utilized to eliminate the dephasing between them. This is verified using stimulated Brillouin scattering with a periodically nonlinear optical fiber that has a period length equal to one-half of the (modulation) wavelength of the intensity waves.     

Classical theory of a free-electron laser

We present a completely classical analysis of the small-signal regime of a free-electron laser. It is explicitly shown that the amplification is due to stimulated scattering produced by a bunching of the electron distribution.     

Theory of intensity noise in semiconductor laser emission

The intensity fluctuations expected in the output of cw semiconductor lasers are studied analytically using linearized multimode rate equations. Spontaneous emission causes intrinsic fluctuations of the laser wave. A power-independent contribution to the intensity fluctuations may occur due to inversion-induced modulation noise. The correlation of the low-frequency noise of different laser modes is investigated. The results are in agreement with experimental data reported in the literature.     

Spectroscopic optical second-harmonic generation from semiconductor interfaces

Optical Second-Harmonic Generation (SHG) from semiconductor interfaces has been widely studied, but it is only recently, with the advent of commercial, tuneable, pulsed laser sources that the spectroscopic aspect of SHG has begun to be more widely exploited. Here, results from porous Si and Si(100)-Sb are reported, which illustrate the potential of spectroscopic SHG as a probe of semiconductor interfaces.Paper presented at the 129th Heraeus Seminar on Surface Studies by Nonlinear Laser Spectroscopies, Kassel, Germany, May 30 to June 1, 1994     

Multimode semiconductor laser with selective optical feedback

We study a multimode semiconductor laser subject to moderate selective optical feedback. The steady state of the laser is destabilized by a Hopf bifurcation and exhibits a period-doubling route to chaos. We also show the existence of a heteroclinic connection between a saddle node and an unstable focus that can be associated with experimentally observed multimode low-frequency fluctuations. This heteroclinic connection coexists with a chaotic attractor resulting from the period-doubling process.     

Classical theory of non-degenerate sum-frequency generation by coherent nonlinear optical mixing of coherent and chaotic radiations

Classical solution of coherent nonlinear optical sum-frequency generation process based on the averaging of stochastic quantities over the initial photocount distributions in sub-frequency radiations is presented in this paper. The evolution of second-order light statistics in sum-frequency generation with coherent and chaotic input radiations is calculated for arbitrary values of the time or space parameter.The author would like to thank Dr. M. Krková from the Computer Centre of Palacky University for performing the numerical calculations.     

Classical theory of non-degenerate sum-frequency generation by incoherent nonlinear optical mixing of coherent and chaotic radiations

The incoherent nonlinear optical sum-frequency generation with non-monochromatic initially uncorrelated sub-frequency input radiations in a dispersive medium is studied in this paper. The efficiency of the process is calculated in the second approximation, whilst the spectral distribution of generated radiation is merely described in terms of the first approximation of the iterative method. The calculations of the efficiency of nonlinear process and the spectral distribution of sum-frequency radiation are performed for one coherent and the other chaotic input radiations, and for both chaotic input radiations, respectively.This work was partially supported by Research Project C.P.B.P. 01. 07.     

外光注入半导体激光器实现时钟分频

从理论和实验上研究了利用光注入半导体激光器对高重复速率光脉冲产生的周期振荡和时钟分频现象.结果表明，光注入半导体激光器引起的二倍周期振荡是使注入脉冲重复频率分频的直接原因.通过耦合速率方程，数值模拟了半导体激光器在外光注入时输出光的时间序列和功率谱，并且分析了激光腔内各种周期振荡的特征.研究表明，当注入光使半导体激光器出现稳定的二倍周期振荡，且注入光的重复频率为此振荡频率的二倍时，时钟分频即可产生实验中，采用重复频率为6.32GHz的光脉冲注入Fabry-Perot激光器，实现了3.16GHz时钟分频信号 关键词： 周期振荡 时钟分频 光谱侧带 光注入     

Noninvasive optical control of complex semiconductor laser dynamics

Time-delayed feedback control (TDFC) is transferred to the optical domain and applied to complex multisection semiconductor lasers as used in optical communication. Pyragas-type control is provided by purely optical feedback from an external Fabry-Pérot interferometer. This all-optical setup needs no time-consuming signal processing and, thus, has practically no speed limit. Proof-of-principle experiments demonstrate noninvasive stabilization of unstable steady states, chaos control, and suppression of noise-induced oscillations on picosecond time scales. A Lang-Kobayashi type model with optical TDFC is investigated taking into account the dynamic details of the device as well as all-optical time-delayed feedback. The parameter regimes that allow for stabilization of stationary emission are mapped out in good agreement with the experiments. Including noise, an analytical expression for the power spectral density is derived, which is confirmed by the experimental all-optical suppression of noise-induced relaxation oscillations.     

Classical theory of optical nonlinearity in conducting nanoparticles

We develop a classical theory of electron confinement in conducting nanoparticles. The theory is used to compute the nonlinear optical response of the nanoparticle to a harmonic external field.     

InGaAsP—InP大光腔结构激光器

本文针对影响InGaAsP-InP激光器温度特性的各种因素,设计并制备了大光腔(LOC)结构激光器.实验表明,这种结构改善了激光器的温度稳定性,获得了低阈值(宽接触型器件J_(th)≈2.5kA/cm~2),高功率(脉冲输出3W)和高特征温度(T_o=150K)器件.     

Simulation on semiconductor optical amplifier intensity noise reduction for future spectrum-sliced optical networks

Spectrum-slicing techniques employing incoherent light are an economic, practical and therefore attractive solution for future all-optical networks, especially for wavelength-division multiplexing (WDM) transmission systems in local area networks (LAN). However, spectrum-sliced methods exhibit a large excess intensity noise factor that limits the performance of the system. In this paper, we investigate noise suppression of spectrum-sliced incoherent light using a saturated semiconductor optical amplifier (SOA). The system incorporating the noise reducing SOA is modeled and simulated using OptSim software, and the results are compared to practical schemes from the literature. Performance comparisons are made with two different broadband sources test-beds. The characteristics of the SOA gain saturation are also presented. In both cases, it is found that a high degree of intensity noise is suppressed by the use of the non-linear gain saturation characteristics of the SOA so as to achieve better system performance. The position of a modulator in the system is also investigated in order to greatly reduce the excess intensity noise.