Widely tunable bottom-emitting vertical-cavity SOAs

We present bottom-emitting tunable vertical-cavity semiconductor optical amplifiers (VCSOAs) with an effective wavelength tuning range of >20 nm. These devices utilize a high reflectivity micromechanically tunable Bragg mirror as the back reflector. Compared with our first generation tunable VCSOAs, the bottom-emitting devices exhibit a two-fold increase in the effective tuning range as well as a five-fold reduction in the required tuning voltage.     

MEMS-tunable vertical-cavity SOAs

We present the signal gain, wavelength tuning characteristics, saturation properties, and noise figure (NF) of MEMS-based widely tunable vertical-cavity semiconductor optical amplifiers (VCSOAs) for various optical cavity designs, and we compare the theoretical results to data generated from a number of experimental devices. Using general Fabry-Pe/spl acute/rot relationships, it is possible to model both the wavelength tuning characteristics and the peak signal gain of tunable vertical-cavity amplifiers, while a rate-equation analysis is used to describe the saturation output power and NF as a function of the VCSOA resonant wavelength. Additionally, the basic design principles for an integrated electrostatic actuator are outlined. It is found that MEMS-tunable VCSOAs follow many of the same design trends as fixed-wavelength devices. However, with tunable devices, the effects of varying mirror reflectance and varying single-pass gain associated with the MEMS-based tuning mechanism lead to changing amplifier properties over the wavelength span of the device.     

Temperature dependence of the relaxation resonance frequency of long-wavelength vertical-cavity lasers

The temperature dependence of the differential gain in AlInGaAs 1310-nm vertical-cavity lasers is investigated. The variations in differential gain and in relaxation resonance frequency are shown to depend on the room-temperature offset between the gain peak wavelength and the wavelength of the lasing mode. The tradeoff between high modulation bandwidth and good high-temperature performance for vertical-cavity lasers is analyzed. A cavity mode that is red-shifted about 25 nm from the gain peak is shown to minimize the variation in modulation bandwidth with temperature, and simultaneously allow for satisfactory high-temperature operation. Experimental results are presented and compared to calculated results with excellent agreement. Because of the change in gain-mode offset with internal temperature, the measured modulation current efficiency changed from about 2 to 4.8 GHz/mA/sup 1/2/ for an increase in drive current from 2 to 10 mA.     

Stable polarization operation of 1.3-/spl mu/m wavelength vertical-cavity surface-emitting laser (VCSEL) fabricated by orientation-mismatched wafer bonding

We present stable polarization of a long-wavelength vertical-cavity surface-emitting laser (LW VCSEL). The polarization control was achieved through growing its active region on a (113)B InP substrate, which was integrated to [001] GaAs-based distributed Bragg reflectors by a wafer-bonding technique. Theoretical investigation showed that to achieve high polarization stability, a large dichroism such as an anisotropic gain is needed. It was also shown that the (113)B and other planes of the (11n) family have asymmetry, which results in asymmetric stress and anisotropic optical gain in a strained multiquantum well. An index-guiding mesa structure was fabricated in an asymmetric shape. The index guiding either enhanced or distracted the polarization stability originating from gain anisotropy, depending on its orientation of the asymmetry, as was confirmed by a statistical summary. Using a VCSEL with an appropriate index-guiding structure, we performed 1-Gb/s modulation and confirmed single polarization under large-signal modulation.     

Noise figure of vertical-cavity semiconductor optical amplifiers

The noise figure of vertical-cavity semiconductor optical amplifiers (VCSOAs) is investigated theoretically and experimentally. Limitations on the noise figure set by the reflectivity of the mirrors are studied. Highly reflective mirrors lead to increased output noise as well as lasing at moderate carrier densities, which imposes a limit on the obtainable population inversion. Expressions for the excess noise coefficient, which governs signal-spontaneous beat noise enhancement due to finite mirror reflectivity, are presented for transmission and reflection-mode operation. Experimental results from a VCSOA operating in the reflection mode at 1.3 μm are presented. The results, from optical as well as electrical measurement techniques, are analyzed and compared to theoretical values     

Small-signal frequency response of long-wavelength vertical-cavitylasers

The small-signal frequency response of long-wavelength vertical-cavity lasers (LW-VCLs) is of interest in determining the ultimate bandwidth of these devices for use in terrestrial networks. This letter analyses two distinct device structures of double wafer-bonded vertical-cavity lasers operating at 1.5 μm and compares their high-speed performance. We demonstrate the highest modulation bandwidth and the highest modulation current efficiency of an electrically pumped LW-VCL of 7 and 4.1 GHz/√mA, respectively     

First demonstration of a MEMS tunable vertical-cavity SOA

We present the first microelectromechanical tunable vertical-cavity semiconductor optical amplifier. The device operates in the long wavelength range and exhibits a minimum of 10 dB of device gain through 11 nm of tuning.     

High-temperature characteristics and tunability of long-wavelength vertical-cavity semiconductor optical amplifiers

In this study, we investigate the high-temperature characteristics and the temperature tuning of long-wavelength vertical-cavity semiconductor optical amplifiers (VCSOA). The temperature shift of the peak-signal gain is shown to depend on the mirror reflectivity of the VCSOA. Experimental results of temperature tuning of a 1.3-/spl mu/m VCSOA are presented. We demonstrate 10 dB of fiber-to-fiber gain over a tuning range of approximately 8 nm.     

1.3-μm vertical-cavity amplifier

We demonstrate the first 1.3-μm vertical-cavity optical amplifier. The amplifier was optically pumped and operated in reflection mode. Optimization of the top mirror reflectivity resulted in a 9.4-dB continuous wave fiber-to-fiber gain, a gain-bandwidth product of 220 GHz, and a saturation output power of -6.1 dBm, all at room temperature. By modulating the pump source, an extinction ratio of 27 dB in the output signal power was obtained     

High output power 1540 nm vertical cavity semiconductor optical amplifiers

Vertical cavity semiconductor optical amplifiers operating at 1540 nm are presented. The use of AlInGaAs multiple quantum well active regions resulted in record-high saturation output power of +0.5 dBm and 16 dB of fibre-to-fibre gain. These results were achieved in reflection mode operation using optical pumping by a 980 nm semiconductor laser.