High-energy (59 pJ) and low-jitter (250 fs) picosecond pulses from gain-switching of a tapered-stripe laser diode via resonant driving

High-energy (59 pJ), low-jitter (250 fs), high-extinction ratio (800), and short (14.5 ps FWHM) pulses were generated by gain-switching of a tapered stripe gain-guided laser diode (LD) via resonant driving. These characteristics are attributed to a stable single-mode near-field pattern, a single-lobe far-field pattern, and multilongitudinal modes associated with the tapered stripe LD under high driving current pulses. These pulses from a comb generator were enhanced mainly from reflection at the LD-transmission line impedance mismatch; the line length was adjusted for resonance with the reflection from the step recovery diode, further increasing the driving current.     

Optoelectronic switches and multigigabit 8:1 time multiplexer

Optoelectronic metal-semiconductor-metal (MSM) switches in InP were studied and used as sampling elements in a digital time division multiplexer. It was found that switch performance can range from the depletion-layer photodiode to the photoconductor regime as the activating light intensity increases. The multiplexer had an 8:1 ratio, a 2-V signal bias, >25-dB S/N, and a serial rate of at least 2.5 Gb/s. This multiplexer with its high S/N and the timing stability intrinsic to fiber delay lines will be advantageous for high-speed digital communications     

Simulation and interpretation of fast rise time light-activatedp-i-n diode switches

A simulation program and a comprehensive physical interpretation for risetimes and output powers of the long transit p-i-n diode under high and low optical-pulse excitations as well as at various impedances are presented. The physical interpretation explains the mechanisms of the switch risetime limitation in terms of the cancellation electric field due to separated photocarriers, the induced electric field with various RC time delays, and the optical-pulse energy risetime. Under high optical excitations and long circuit risetimes, the output risetime is determined only by the electric field cancellation time associated with the collapse of the total electric field and decreases with increasing optical-pulse excitation. This is in contrast to the case of low optical-pulse excitations where the risetime is determined by both the circuit risetime and the optical-pulse energy risetime     

Photo-injection p-i-n diode switch for high-power RF switching

The high RF power-switching properties of the photo-injection p-i-n switch (PIPINS), an optically controlled RF switch, are investigated. Proper functioning of a PIPINS as a low insertion-loss RF switch requires that it operates as a photoconductor, where the photo-injected charge is much greater than the RF sweep out charge. Insertion loss using 650-mW optical power was <0.4 dB at RF (VHF-UHF) power in excess of 200 W, and devices successfully standoff 200-W incident RF power with the series isolation being determined by the device capacitance (e.g., 225 fF). PIPINS hot-switching measurements are reported for the first time, with output RF power up to 180 W at low duty cycle, rise times of 1 ps, and fall times for a series shunt switch of ≈2.5 μs. The RF power for hot switching a PIPINS is limited by a latch-on effect, which is dependent on a variety of parameters, including duty cycle and repetition period, consistent with thermally generated carriers contributing to the latch-on effect. The switching properties of PIPINS make them a candidate for high RF power applications such as reconfigurable antennas, where electromagnetic isolation of the switch and control lines are critical     

Photovoltaic-p-i-n diodes for RF control-switching application

A photovoltaic-p-i-n diode switch, consisting of two back-to-back p-i-n diodes which can be forward biased to the ON state by photovoltaic cell photocurrents, is introduced for optically controlling RF signals. Without light, the switch is in the OFF state and isolation is determined by the diode junction capacitance. We report a device operating in the VHF range and handling 25 W. With 40 mA photocurrent injected into each diode, the measured insertion loss at 25-W input power is ≈0.08 dB, mainly limited by the diode series resistance; its capacitance was 380 fF. Experiments indicate that low insertion loss requires the signal period ≪ carrier lifetime so that carrier sweep out in the I-region does not reduce conductivity     

Optoelectronic time division multiplexing

The concept of using optoelectronic (photoconductive) switches as the sampling element in time division multiplexing is introduced in the context of VLSI off-chip data transmission. A 4:1 multiplexer was fabricated in Cr : GaAs, activated by a GaAs laser via optical fibre delay lines and operated at 2.5 Gbit/s.