Mixing In Semiconductor Laser Research Articles

Dual-pumped nondegenerate four-wave mixing in semiconductor laser with a built-in external cavity

In this paper, a semiconductor laser system consisting of a conventional multimode Fabry–Pérot laser diode with a built-in external cavity is presented and demonstrated. More than two resonance modes, whose peak levels are significantly higher than other residual modes, are simultaneously supported and output by adjusting the bias current and operating temperature of the active region. Based on this device, dual-pumped nondegenerate four-wave mixing—in which two pump waves and a single signal wave are simultaneously fed into the laser, and the injection power and wavelength of the injected pump and signal waves are changed—is observed and discussed thoroughly. The results show that while the wavelengths of pump wave A and signal wave S are kept constant, the other pump wave B jumps from about 1535 nm to 1578 nm, generating conversion signals with changed wavelengths. The achieved conversion bandwidth between the primary signal and the converted signal waves is broadly tunable in the range of several terahertz frequencies. Both the conversion efficiency and optical signal-to-noise ratio of the newly generated conversion signals are adopted to evaluate the performance of the proposed four-wave mixing process, and are strongly dependent on the wavelength and power of the injected waves. Here, the attained maximum conversion efficiency and optical signal-to-noise ratio are close to −22 dB and 15 dB, respectively.

Concept of internal mixing in semiconductor lasers and optical amplifiers for room-temperature generation of tunable continuous terahertz waves

We discuss the potential for creating a tunable continuous-wave source for the 1–5 THz frequency range based on nonlinear mixing in the active medium of a dual-color semiconductor laser or laser amplifier. Our analysis for the 1.55 μ m wavelength regime shows that intracavity mixing, after minimization of THz waveguide losses and optimization of the second-order nonlinearity of the active medium, should provide up to 100 μ W of THz power at an optical power of 100 mW per color.

Concept of Internal Mixing in Semiconductor Lasers and Optical Amplifiers for Room-Temperature Generation of Tunable Continuous TeraHertz Waves

Concept of Internal Mixing in Semiconductor Lasers and Optical Amplifiers for Room-Temperature Generation of Tunable Continuous TeraHertz Waves

Optical phase conjugation in laser diodes subjectto strong probe injection power

Nearly degenerate four-wave mixing in semiconductor lasers is experimentally studied for different probe injection powers. It is shown, in accordance with theoretical predictions, that the reflectivity efficiencies of probe and conjugate waves demonstrate significantly different behaviour for strong probe injection power, compared with small probe power. Nearly uniform conversion efficiency of order 20-30 dB for frequency detuning up to 3 GHz is achieved at /spl sim/0.8 /spl mu/W launched probe power.

Carrier diffusion and depletion effects on multiwave mixing in semiconductor lasers

A detailed theoretical treatment has been undertaken of multiwave mixing in semiconductor lasers, taking into account the effects of pump/probe depletion, carrier diffusion, usual gain saturation, nonlinear gain compression, total power dependence of the coupling coefficients as well as the longitudinal dependence of the nonlinear interaction. It is shown that the effect of carrier diffusion can considerably enhance the probe and conjugate reflectivity for detuning frequency near the relaxation oscillation frequency of the pump laser. It is demonstrated, in particular that, for relatively high input probe power, the probe and conjugate reflectivity can be enhanced significantly near the relaxation oscillation frequency of the pump laser, compared to that for low input probe power. Furthermore, both the probe reflectivity and the conjugate reflectivity show asymmetric characteristics with respect to the zero pump/probe frequency detunings. The pump/probe depletion effect plays an important role in determining the optical output power when the input probe power is larger than /spl sim/0.1 /spl mu/W.

Nanometer wavelength conversion of picosecond-optical pulses using cavity-enhanced highly nondegenerate four-wave mixing in semiconductor lasers

We demonstrate 5.0-nm wavelength conversion of a mode-locked optical pulse train by cavity-enhanced highly nondegenerate four-wave mixing in a 1.53-/spl mu/m injection-locked bulk InGaAsP V-groove laser. Input pulses having 17 ps duration are broadened to 61 ps due to the filtering imposed by the mixing laser. A simple two-mode rate equation model of an injection-locked semiconductor laser is used to explain the dependence of the output pulse broadening on bias current and injected pump power. The temporal response is improved by decreasing the laser bias current or increasing the injected pump power. >

Optoelectronic microwave-range frequency mixing in semiconductor lasers

Optoelectronic mixing of very high-frequency amplitude-modulated signals using a semiconductor laser simultaneously as a local oscillator and a mixer is proposed, Three possible constructions of a monolithically integrated up-or down-converter are considered theoretically: a four-terminal semiconductor laser with dual pumping current/modal gain control, and both a passively mode-locked and a passively Q-switched semiconductor laser monolithically integrated with an electroabsorption pumping current modulator. Experimental verification of the feasibility of the laser-mixer concept is presented. >

Density matrix model for highly nondegenerate four-wave mixing in semiconductor laser devices

A model for highly nondegenerate fourwave mixing in semiconductor lasers has been implemented, with possible application to amplifiers operating under multifrequency optical fields and to oscillators used for frequency conversion. Fast phenomena, such as spectral hole burning and hot carrier effects, are accounted for in a unified approach through the density matrix formalism. Hence, the model is suitable for evaluating frequency mixing effects over a very wide range of beat frequency, starting from zero up to thousands of gigahertz. Interest in these phenomena has increased in recent years, both for the analysis of basic material characteristics and for application to devices for multichannel coherent optical communication systems. As an example, the model has been used to compute intermodulation effects in a travelling-wave amplifier, under multicarrier operation. The numerical simulation results are in satisfactory agreement with experimental measurements recently reported in the literature.

Observation of nearly degenerate and cavity-enhanced highly nondegenerate four-wave mixing in semiconductor lasers

Both nearly degenerate four-wave mixing (FWM) and cavity-enhanced highly nondegenerate four-wave mixing have been studied in a GaAs/AlGaAs semiconductor laser operated above threshold. It is observed that the cavity-enhanced highly nondegenerate FWM signal is of the same order as the nearly degenerate FWM signal. A four-wave mixing signal enhancement of about 90 dB as compared to the background signal is observed at the pump-probe detuning corresponding to the round-trip frequency of the pump laser. The probe amplification is measured in the same frequency range and a large enhancement is also observed.

Phase noise of four-wave mixing in semiconductor lasers

A simple theoretical analysis shows that the linewidth of the conjugate wave produced in four-wave mixing in semiconductor lasers is equal to the linewidth of the probe plus four times the linewidth of the pump. Experimental results in good agreement with the theory are presented. This result implies an enormous enhancement in the phase noise of the conjugate wave and sets a limitation on some practical applications of four-wave mixing.

Population pulsations and nondegenerate four-wave mixing in semiconductor lasers and amplifiers

The theory of nondegenerate four-wave mixing (NDFWM) in semiconductor lasers and amplifiers is presented with particular emphasis on the physical processes that lead to population pulsations. In the case of nearly degenerate four-wave mixing, modulation of the carrier density at the beat frequency Ω of the pump and probe waves creates a dynamic population grating whose effectiveness is governed by the spontaneous carrier lifetime τs. Such a grating affects both the gain and the refractive index of the probe wave. In particular, the probe gain exhibits features analogous to those observed in a detuned atomic system arising from the optical Stark effect. Both the gain grating and the index grating contribute to NDFWM, with the dominant contribution coming from the index grating. For detunings such that Ωτs ≫ 1, population pulsations correspond to modulation of the intraband population arising from spectral hole burning. Our results show that NDFWM is then limited by the phase-mismatch effects governed by the transit time τ rather than by the intraband population-relaxation time T1. Significant NDFWM is expected to occur for detunings up to about 300 GHz for typical transit-time values of 3 psec in semiconductor lasers.

Cascade four-wave mixing in semiconductor lasers

Highly efficient cascade frequency mixing signals are generated in a nearly degenerate intracavity four-wave mixing experiment in a GaAs/(GaAl)As semiconductor laser. This method allows a consistent quantitative determination of the third-order nonlinear optical susceptibility within the gain bandwidth of a semiconductor laser. The dependence of this susceptibility on light intensity reveals the contribution of the free-carrier plasma.

Highly nondegenerate four-wave mixing in semiconductor lasers due to spectral hole burning

Spectral hole burning in semiconductor lasers manifests as a nonlinear suppression of the mode gain by a few percent. In the presence of a probe wave, the same mechanism can lead to highly nondegenerate four-wave mixing (NDFWM) by creating the dynamic gain and index gratings at the beat frequency of the pump and probe waves. Since the grating efficiency is governed by the intraband relaxation time (typically <1 ps), significant NDFWM can occur even for a pump-probe detuning ∼100 GHz. We present the results for the conjugate reflectivity and the probe transmittivity when an InGaAsP laser is used as a traveling-wave amplifier.