Ta-Chung Wu

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.

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.

Resonant modulation of single contact monolithic semiconductor lasers at millimeter wave frequencies

Resonant modulation of a single contact semiconductor laser at the cavity roundtrip frequency of 40 GHz is demonstrated. Efficient mode coupling is obtained with a single contact device by utilizing the high attenuation of the millimeter‐wave modulation signal along the laser stripe. The properties and limitations of this technique are analyzed using a distributed circuit model of the laser.

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.

Characteristics of longitudinal optical phonon assisted quantum carrier capture process‐temperature and bias dependence

The quantum carrier capture time in a quantum well laser is calculated as a function of temperature and bias current. The calculated results show good consistency with recent measurements on the small signal frequency response of a quantum well laser at cryogenic temperatures. This calculation reveals some of the characteristics of longitudinal optical phonon assisted quantum carrier capture phenomena in quantum well structures.

Millimeter wave signal transmission using uncoated telecommunications-grade distributed feedback lasers

Summary form only given. In conclusion, we have demonstrated efficient fiber-optic transport at mm-wave frequencies using an uncoated single contact DFB laser. These results indicate that simple, low-cost mm-wave optical transmitters can be constructed for fiber-fed antennas in mm-wave wireless picocellular networks and mm wave phased-array antenna systems.

Optical transmission of narrowband mm-wave signals using telecommunications-grade DFB lasers

Using an uncoated monolithic single-contact distributed feedback (DFB) laser, transmission of 2 Mb/s data at a subcarrier frequency of 35 GHz over 2.2 km of optical fiber by resonant modulation is demonstrated. Modulation response of 60 MHz with more than 1 GHz of enhancement at round trip frequency, carrier-to-noise ratio and bit-error-rate results are reported. The tolerance of the resonant round-trip frequency to the DFB facet cleaving process and the device length uncertainty due to cleaving is also addressed in detail by computer simulation.

Transmission of millimeter-wave signals using uncoated telecommunications-grade distributed feedback lasers

Transmission of 2-Mb/s data at a subcarrier frequency of 35 GHz over 2.2 km of optical fiber by resonant modulation of an uncoated monolithic single-contact distributed feedback (DFB) laser is demonstrated. Modulation response, carrier-to-noise ratio and bit-error-rate results are reported. The tolerance of the resonant round-trip frequency to the DFB facet cleaving process and the device length uncertainty due to cleaving is also addressed in detail by computer simulation.