Sidney C. Kan

On the effects of carrier diffusion and quantum capture in high speed modulation of quantum well lasers

It is shown that, the combined effects of carrier diffusion in the separate confinement heterostructure region and quantum capture into the quantum well must be considered together when evaluating the limits on the modulation bandwidth of quantum well lasers, despite the fact that quantum capture is considerably faster than carrier diffusion. The importance of quantum capture may be observed by noting that the modulation bandwidth is adversely affected even for quantum capture times as short as 0.2 ps, or if the ratio of the quantum capture time to quantum escape time is large (≳0.01). Therefore, the bandwidth limitation may be caused by electron transport rather than hole transport since quantum capture of holes is faster than that of electrons.

Quantum capture and escape in quantum-well lasers-implications on direct modulation bandwidth limitations

Analytic expressions for carrier capture and escape currents into quantum wells are derived. The authors find that the escape rate can be as large as the capture rate under typical operating conditions in quantum-well lasers so that the damping and inertia of the relaxation oscillation are significantly increased in these lasers. Implications for the limitation of the modulation bandwidth of quantum-well lasers and its dependence on the quantum-well structure are discussed.<<ETX>>

Quantum capture limited modulation bandwidth of quantum well, wire, and dot lasers

We investigate the quantum capture limited modulation bandwidths of various lower‐dimensional semiconductor lasers. It is shown that, for buried quantum well, wire, and dot lasers, the maximum bandwidth is proportional to the packing density of the active region. For the quantum wire lasers grown on V‐grooved substrates, the maximum bandwidth is enhanced by the precapture of carriers from three‐dimensional states to two‐dimensional states before the capture into the one‐dimensional states.

Intrinsic equivalent circuit of quantum-well lasers

An intrinsic equivalent circuit of quantum-well lasers that takes the capture of carriers into the quantum well into account is presented. Several qualitative features in the modulation response and the device impedance are revealed. The dependences on the carrier capture and escape rates are discussed.<<ETX>>

Gain compression in tensile‐strained 1.55 μm quantum well lasers operating at first and second quantized states

Gain compression coefficients in tensile‐strained 1.55 μm single quantum well lasers are measured using an optical injection method. Lasers operating in the first and second quantized states are used. An explicit linear dependence of nonlinear gain on the differential gain is obtained from these measurements. These results are quantitatively compared to a recently proposed model involving carrier transport in and out of the quantum well.

Surface-micromachined Movable SOI Optical Waveguides

We demonstrate the fabrication and the micromechanical motion of a new type of optical waveguides, the surface-micromachined movable SOI optical waveguides. The movable waveguides are either in form of cantilevers and bridges. The fabrication process is based on conventional IC technology. Deflection amplitude of 1400/spl mu/m for cantilevers guiding lightwave of 1.3/spl mu/m wavelength is observed. Waveguide loss of less than 1.8dB/cm with a 10% polarization dependence is achieved.

Micromechanical optical switching with voltage control using SOI movable integrated optical waveguides

Optical switching is demonstrated using movable integrated optical waveguides fabricated on silicon-on-insulator substrates. The switching effect is produced by the voltage-controlled micromechanical deflection of the movable waveguides. The dynamic response of the deflection is studied. A contrast ratio of 12 dB of switching is obtained using an applied voltage of less than 10 V. At 20 V, the contrast ratio is about 40 dB.<<ETX>>

Influence of separate‐confinement layer band structure on the transport‐limited modulation bandwidth in quantum well lasers

We analyze the influence of band‐structure design of the SCH region on the transport‐limited modulation bandwidth in quantum well (QW) lasers. By properly grading the SCH region, limitations due to physical‐space transport can largely be removed. Limitations due to intrinsic quantum capture (state‐space transport) then becomes the dominant one for GRINSCH QW lasers, though this, too, can be alleviated (but only completely removed) by proper band‐structure design.

Optical control of resonant tunneling diode monolithically integrated with PIN photodiode

Optical control of the resonant tunneling characteristics of an integrated optoelectronic device with a monolithic integrated double-barrier/PIN structure is studied. Optical switching of the bistable resonant tunneling state and optical injection locking of a resonant tunneling oscillator at 1 GHz are demonstrated.

Spontaneous emission measurements for resolving damping mechanisms in direct modulation of quantum well lasers

We demonstrate a measurement technique for determining the contribution of carrier transport effect on the maximum modulation bandwidth in quantum well lasers. This technique independently measures the ratio of the effective carrier capture to escape times, as well as the contribution from intraband damping mechanisms, in an operating laser. Every single parameter in the present model for modulation dynamics of quantum well lasers can now be determined experimentally, which enables a consistency check on its validity.