Semiconductor Laser Amplifier Research Articles

Improved operation characteristics of long-wavelength lasers using strained MQW active layers

Long-wavelength semiconductor lasers and amplifiers with strained MQW structures as active layer materials in the region of 1.48-1.55 /spl mu/m are reported. Various improvements in device performance by employing the strained MQW structures were experimentally demonstrated in high-power operation at 1.48 /spl mu/m, high-speed operation with narrow linewidth at 1.55 /spl mu/m, and polarization-insensitive optical amplification in the 1.5 /spl mu/m band. A compressively strained InGaAsP/InGaAsP MQW structure was used for high-power operation. The maximum power could be increased by introducing a compressive strain into the well layers, as theoretically predicted. This increase can be attributed to the suppression of Auger nonradiative recombination and intravalence band absorption. High-speed characteristics were tested on two different active layer materials. The compressively strained InGaAsP/InGaAsP MQW structure proved to be better than the strained InGaAs/InGaAsP MQW structure as an active layer material because of its high differential gain at low threshold current due to a smaller valence band density of states and small carrier life time. Compressively strained InGaAs/AlGaInAs MQW structure, having larger quantum confinements due to larger band offsets than the InGaAsP-based structures, were employed for the high-speed laser. The relaxation frequency was estimated to be 26 GHz, and a small linewidth enhancement factor of 1.5 was obtained. Polarization insensitive optical amplification in the semiconductor laser amplifiers (SLAs) was demonstrated by using the tensile strained MQW structure. The device length and strain were optimized for polarization insensitive amplification.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Two-section Semiconductor Laser Amplifier used as Phase Modulator in a DPSK Heterodyne System

Article Two-section Semiconductor Laser Amplifier used as Phase Modulator in a DPSK Heterodyne System was published on June 1, 1994 in the journal Journal of Optical Communications (volume 15, issue 3).

Analysis of gain and saturation characteristics of a semiconductor laser optical amplifier using transfer matrices

The transfer matrix method (TMM) has been applied to analyze the gain and saturation characteristics of semiconductor laser optical amplifiers. This method approximates the amplifier cavity by dividing it into M discrete subsections, and TMM has been applied to analyze the stepwise longitudinal field distribution at each subsection along the amplifier cavity. By incorporating also the carrier rate equations into the analysis, it has been shown that the approximation can accurately describe the carrier density and longitudinal field distribution along the amplifier cavity if M is sufficiently large (i.e., the size of each subsection is about an order of magnitude of one wavelength of the input signal). By assuming that the amplifier is biased below oscillation threshold such that the contribution of spontaneous emissions to the gain characteristics can be neglected, we have shown that our proposed method yields a fast and efficient algorithm in analyzing the gain and saturation characteristics of laser amplifiers. We have compared the results produced by our method to those analyzed using the average photon density (AVPD) approximation technique, as well as to experimental results on a 1.5-/spl mu/m buried heterostructure semiconductor laser amplifier. >

Deformation of signal in nearly degenerate four-wave mixing with travelling-wave semiconductor laser amplifiers

A theoretical analysis is given to demonstrate the behavior of the deformation of a signal in nearly degenerate four-wave mixing with travelling-wave semiconductor laser amplifiers.

Effects of stray reflections on the performance of semiconductor laser amplifiers as in-line optical repeaters

The effects of stray reflections from the ends of optical fibres on the gain and spontaneous emission of a semiconductor laser amplifier have been analysed. The transfer matrix method (TMM) has been applied to give efficient solutions to the problem. The theoretical results show that these stray reflections can seriously deteriorate the performance of a single amplifier and can degrade the overall performance of a system incorporating a cascaded chain of amplifiers as in-line repeaters.

Compact 40 Gbit/s optical demultiplexer using a GaInAsP optical amplifier

A polarisation insensitive GaInAsP near travelling wave semiconductor laser amplifier is used as the nonlinear element in a nonlinear optical loop mirror. With this compact configuration, the authors demonstrate a continuously tunable switching window, and report, for the first time using semiconductor materials, error ratio measurements for a demultiplexing operation from 40 to 10 Gbit/s, with a receiver sensitivity of −23 dBm.

Wavelength conversion and switching of high speed data signals using semiconductor laser amplifiers

Nonlinear gain dynamics in semiconductor laser amplifiers enables ultrafast signal processing. Wavelength conversion of up to 18 Gbit/s data signals is demonstrated. The switching characteristics are applied to the operation of an AND gate for 30 ps pulses.

Observation of dynamic frequency chirp in dispersive nonlinear semiconductor laser amplifiers

We present a first direct experimental observation of dynamic frequency chirp associated with the turn-on spike in the output of a Fabry–Perot semiconductor laser amplifier. Such a frequency chirp exists because of the change in the refractive index at the onset of light injection due to carrier saturation. The experimental observation is made by using a novel technique to optically isolate the turn-on spike from the steady-state response level. Using this technique, we have also successfully demonstrated conversion of a high duty-cycle data stream to a low duty-cycle data stream of the same frequency, which could have potential applications in optical time division multiplexing.

High-power high-gain monolithically integrated preamplifier/power amplifier

The monolithic integration of an index-guided single lateral mode optical preamplifier with a power tapered semiconductor laser amplifier is reported. With a coupled input power of only 6 mW, 4.5W of output power is obtained at 810nm. The far-field pattern is dominated by a diffraction-limited single lobe. An internal small signal gain of 35dB is demonstrated.

Compensation fibre chromatic dispersion by optical phase conjugation in a semiconductor laser amplifier

Spectral inversion in a semiconductor laser amplifier has been used, for the first time to the authors&apos; knowledge, to achieve compensation of the chromatic dispersion in singlemode fibre. This was demonstrated by transmission of a directly modulated, highly chirped 2.5Gbit/s signal at 1.5μm across 100km of normal dispersion fibre.

A simple method to determine carrier recombinations in a semiconductor laser optical amplifier

The contribution of nonradiative carrier recombinations to the characteristics of long-wavelength InGaAsP/InP semiconductor laser devices is verified by measuring the amplified spontaneous emission (ASE) power from a 1.5- mu m semiconductor laser amplifier (SLA) against the bias current. This method provides a simple and straightforward way to determine the mathematical form of recombination rate in a long-wavelength semiconductor laser, provided that the structural parameters of the laser are known.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Real-time in situ ellipsometric control of antireflection coatings for semiconductor laser amplifiers using SiOx

We demonstrate an innovative technique based on real-time in situ ellipsometry to achieve precise monitoring and control of the refractive index of antireflection coatings for semiconductor laser amplifier facets. The refractive index and the layer thickness are extracted every 0.5 s using two thin-film models: the conventional four-medium model which provides an averaged refractive index over the total deposited film, and an adaptive multilayer model which keeps tract of all the previous thin layers that have been deposited and provides a sensitive and instantaneous response to any new refractive index change. A simple procedure to account for polarization effects due to strain in the windows of the evaporator is also described. Using the weighted average of the refractive indices obtained with these two techniques as a feedback parameter, control of the averaged refractive index of SiOx deposited films within ±0.01 and facet reflectivities of order 10−4 or better are reproducibly obtained.

Ultrashort pulse reshaping using a semiconductor laser amplifier in a ring cavity

We describe an interferometric method for the reshaping and amplification of a mode-locked train of short laser pulses, based on a ring cavity containing a semiconductor laser amplifier. The amplifying medium provides both the gain and the phase nonlinearity needed for pulse reshaping. Numerical simulations have shown that the best reshaping occurs with the use of a low finesse cavity operated at laser threshold. Upon these conditions, calculations have shown that both pulse compression and amplification are obtained over a broad range of values of the linear phase shift between the cavity and pulse train. Pulse amplification and compression factors exceeding 50 and 100, respectively, resulting in peak power amplification factors up to 1000, are predicted for a 25 dB amplifier. These factors can be increased by decreasing the ratio of the input pulse energy over the saturation energy of the amplifier.

Multiple-quantum-well GaInAs/GaInAsP tapered broad-area amplifiers with monolithically integrated waveguide lens for high-power applications

A 1.48- mu m tapered broad-area semiconductor laser amplifier with a monolithically integrated waveguide lens as demonstrated. The gain saturation characteristics of the tapered amplifier were examined. A maximum output power of 300 mW and a 3-dB saturation power of 200 mW under quasi-CW conditions were obtained from the amplifier without the waveguide lens. Output power of 200 mW was obtained with a broad emission spectrum of approximately 30 nm when the device was used as a superluminescent diode. The amplified output was focused to a single lobe by the monolithically integrated aspheric waveguide lens, which may be useful for efficient coupling of the output into a single-mode fiber.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Characterization of an InGaAsP semiconductor laser amplifier as a multifunctional device

Multifunctional properties of an InGaAsP semiconductor laser amplifier have been evaluated. A bit error rate of 10/sup -9/ at 100 Mb/s was obtained using the amplifier as a detector at a received optical power of -27 dBm with simultaneous cavity gain of 16 dB. The bandwidth of the amplifier detector was 300 MHz and the maximum responsivity was 30 V/W. The amplifier had a maximum gain of 29 dB and a very large optical on/off ratio of 50 dB. When the amplifier was used as a switch the cavity gain was 19 dB and the extinction ratio was 22 dB.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

All-optical high speed demultiplexing with a semiconductor laser amplifier in a loop mirror configuration

A novel, purely optical technique for demultiplexing high speed time-division multiplexed data is demonstrated. The technique uses the SLALOM (semiconductor laser amplifier in a loop mirror). The data rate is not limited by the gain recovery time of the semiconductor laser amplifier. The same technique can also be used for multiplexing.

Digital transmission experiment with monolithic 4 × 4 InGaAsp/InP laser amplifier gate switch array

Digital transmission experiments at 2.488 Gbit/s involving a monolithic 4 × 4 semiconductor laser amplifier gate switch array operating at around 0 dB fibre-to-fibre gain have been performed. Receiver power penalties less than 1 dB are reported for a switch input power range in excess of 10 dB. Results on switch saturation include a switch signal output power, coupled to the output fibre, of – 5 dBm for 3 dB gain compression of the 4 × 4 switch.

Time slot interchanging using semiconductor laser amplifiers

A four-channel optical time slot interchange switching experiment operating at 2.5 Gbit/s is reported. The system is based on a parallel switch fabric incorporating semiconductor laser amplifier gates and fibre delay lines. A sensitivity penalty of 0.2 dB for straight through operation, and 0.7 dB for fully interchanged time slots was observed. >

Numerical analysis of flared semiconductor laser amplifiers

A numerical model for flared semiconductor optical amplifiers that incorporates the effects of gain and index saturation and thermal effects is presented. Theoretical near fields, far fields, and quadratically phase-corrected far fields are presented. The results indicate that flared semiconductor laser amplifiers are capable of coherent diffraction-limited output powers in excess of 1 W CW. >

Multiterahertz frequency conversion of a picosecond pulse train using nonlinear gain dynamics in a 1.5 μm MQW semiconductor laser amplifier

The femtosecond nonlinear gain dynamics in semiconductor laser amplifiers were used for the 3.8 THz frequency conversion of 30 ps pulses by four-wave mixing.