This paper overviews the properties and possible applications of long wavelength vertical-cavity semiconductor optical amplifiers (VCSOAs). A VCSOA operating in the 1.3-/spl mu/m wavelength region is presented. The device was fabricated using wafer bonding; it was optically pumped and operated in reflection mode. The reflectivity of the VCSOA top mirror was varied in the characterization of the device. Results are presented for 13 and 12 top mirror periods. By reducing the top mirror reflectivity, the amplifier gain, optical bandwidth, and saturation output power were simultaneously improved. For the case of 12 top mirror periods, rye demonstrate 13-dB fiber-to-fiber gain, 0.6 nm (100 GHz) optical bandwidth, a saturation output power of -3.5 dBm and a noise figure of 8.3 dB. The switching properties of the VCSOA are also briefly investigated. By modulating the pump laser, we have obtained a 46-dB extinction ratio in the output power, with the maximum output power corresponding to 7-dB fiber-to-fiber gain. All results are for continuous wave operation at room temperature.

Long wavelength vertical-cavity semiconductor optical amplifiers

We demonstrate second-harmonic generation in a doubly resonant semiconductor microcavity. The monolithic cavity consists of an AlGaAs active medium sandwiched between two AlGaAs/AlAs dual-wavelength mirrors. The mirrors do not have any apparent periodicity because, unlike single- or dual-wavelength Bragg reflectors, they are engineered with dispersion taken into account. Quasi-phase matching is obtained by addition of the appropriate phases at reflection so as to compensate for the dephasing between the fundamental and the second-harmonic fields.

Second-harmonic generation in a doubly resonant semiconductor microcavity.

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.

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MEMS-tunable vertical-cavity SOAs

We report on the first experimental realization of a multifunctional long wavelength /spl lambda/=1.5-/spl mu/m InGaAsP MQW vertical cavity laser amplifier-photodetector. An optical gain of up to 18 dB and a voltage responsivity of 160 V/W is demonstrated.

Experimental demonstration of a multifunctional long-wavelength vertical-cavity laser amplifier-detector

We present experimental measurements of bistable characteristics for the case of a 1.55-/spl mu/m symmetric Fabry-Perot laser amplifier with a particularly rich variety of behavior for reflected signals. Three main forms of hysteresis loops are observed on reflection. The hysteresis loop changes from anticlockwise to clockwise hysteresis in the optical output-input characteristic when the drive current or initial phase detuning is changed. A "butterfly" hysteresis loop is observed experimentally at an optical input power as low as 300 /spl mu/W for a drive current equal to 94% of the lasing threshold. The dependence of the reflective optical bistability on drive current, initial phase detuning, and injected optical pewter has been investigated for the first time in an uncoated 1.55-/spl mu/m amplifier. Measurements of the device voltage shifts on switching reveal hysteresis loops which match those in the corresponding optical powers and which indicate the amount of gain saturation and nonlinear refraction responsible for bistability. An analytical model is used to describe the observed reflective bistability and to give insight into the detailed physical mechanisms responsible.

Measurements and modeling of reflective bistability in 1.55-/spl mu/m laser diode amplifiers

A 30 dB gain with multi‐GHz modulation bandwidth is obtained in an optically pumped vertical cavity Fabry–Perot structure. This device may be called a vertical cavity amplifying photonic switch (VCAPS). The amplification configuration has been used for a direct measurement of the carrier induced refractive index change over the absorption as well as the gain regime.

Vertical cavity amplifying photonic switch

Optical amplification by stimulated emission is achieved in a vertical microcavity. A fast response of 20 ps and a gain of 2.5 dB point to an optical switch with a modulation width > 10 GHz, capable of handling 2 THz signals.

Vertical microcavity optical amplifying switch

S. D. Brorson, J. Zhang, S. R. Keiding, Odense Universitet, DK-5230 Odense M , Denmark We have performed two different types of femtosecond pump and probe measurements on THz transmitting antennas.' The devices were "10-?;0-10" antennas fabricated on ion-bombarded silicon-onsapphire (SOS) chips and pumped with a mode-locked Ti:A120, laser. The experimental setup is similar to the usual configuration for THz spectroscopy* except that the transmitting antenna is excited by two laser pulses, a "pump" and a "probe."2 The emitted THz pulse is monitored ai the receiving a.ntenna by activating the receiver with a "gate" pulse from the laser. In the first measurement, the time delay T between the pump and probe pulses at the transmitter is fixed, and the time behavior of the emitted THz pulse is measured at the receiving antenna by scanning the gate time T. 'The pump beam is chopped at frequencyf, (typically -1 kHz), and the THz pulse is detected using a lock-in amplifier tuned to the same frequency, f,. The results are shown in Fig. 1, where the delay of the probe pulse at the transmitter has beten stepped over a range T -6 ps to i 6 ps. The THz pulse radiated by the pump beam is clearly visible at T = 0. Visible also is a signal due to the probe, which can be seen at successive positions in the scan. Since the probe beam is unchopped, and we are detecting only signals atf, with the lock-in, this signal originates as an intermodulation between the pump and probe pulses. Further experiments have indicated that it is due to screening from photoexcited carriers. Furthermore, since the probe signal is present and of equal size for both T > then recombine over a nanosecond time period. We present a simple analytical model, which is consistent with the experimental observations.

M. Bensoussan

Papers

Vertical cavity amplifying photonic switch

Vertical microcavity optical amplifying switch

30 dB gain in vertical cavity amplifying photonic switch