M.G. Young

Tapered waveguide InGaAs/InGaAsP multiple-quantum-well lasers

The use of ultrathin etch-stop techniques to expand the vertical optical mode size adiabatically in 1.5- mu m InGaAs/InGaAsP MQW lasers using a tapered-core passive intracavity waveguide structure is discussed. 30% differential quantum efficiency out the tapered facet, far-field FWHM of approximately 12 degrees and a butt-coupling efficiency into a cleaved fiber of -4.2 dB, with -1-dB alignment tolerances of approximately +or-3 mu m, were achieved.<<ETX>>

A 16*1 wavelength division multiplexer with integrated distributed Bragg reflector lasers and electroabsorption modulators

The integrated operation of a 16*1 wavelength-division-multiplexed (WDM) source with distributed Bragg reflector (DBR) lasers and electroabsorption modulators has been demonstrated. By using repeated holographic exposures and wet chemical etching, 16 different wavelengths from 1.544 to 1.553 mu m with an average channel spacing of 6 AA are obtained. A high-performance combiner is used to obtain a very uniform coupling into the single-output waveguide, and with the integration of an optical amplifier an average optical power of -8 dBm per channel is coupled into a single-mode fiber.<<ETX>>

Electric field screening by photogenerated holes in multiple quantum wells : a new mechanism for absorption saturation

We observe saturation in the electroabsorption of InGaAs/InP multiple quantum wells (MQWs) at high optical intensity. Contrary to the mechanism for zero‐field MQWs, we find that saturation occurs due to the presence of trapped photogenerated holes that screen the MQWs from the applied electric field. By carefully measuring the absorption coefficient of the wells and the emission time for holes, we are able to fit the observed electroabsorption saturation with no adjustable parameters.

Strain-compensated strained-layer superlattices for 1.5 μm wavelength lasers

Strain‐compensated strained‐layer multiple quantum well structures have been grown by introducing opposite strain into the barrier layers. Such structures show significant improvement in the photoluminescence spectra, i.e., narrower full width half maxima and stronger intensities. Lasers fabricated with such structures have exhibited low current thresholds (12 mA), high quantum efficiencies (28% per facet), which are constant over a wide current range.

1.5 mu m multiquantum-well semiconductor optical amplifier with tensile and compressively strained wells for polarization-independent gain

A multiquantum-well optical amplifier for 1.5- mu m wavelength operation using alternating tensile and compressively strained wells in the active region is described. For each bias level measured, the polarization sensitivity of the amplifier gain is 1 dB or less averaged over the gain bandwidth. This amplifier is suitable for integration with other optical devices in photonic integrated circuits which require polarization-independent gain.<<ETX>>

Digitally tunable laser based on the integration of a waveguide grating multiplexer and an optical amplifier

A novel monolithic semiconductor laser is demonstrated. The optical cavity comprises a 1/spl times/N waveguide grating multiplexer connected to N optical amplifiers. By driving a specific output port, laser oscillation is obtained at the wavelength determined by the wavelength path through the multiplexer. Such a laser is very useful for WDM systems because it is capable of producing a comb of precisely spaced frequencies.<<ETX>>

5.5-mm long InGaAsP monolithic extended-cavity laser with an integrated Bragg-reflector for active mode-locking

A 5.5-mm-long monolithic extended-cavity laser with an integrated Bragg-reflector in the InGaAsP system for active mode-locking at low repetition rates at a wavelength of 1.55 mu m has been fabricated. The device, which is designed to be used as a pulse source in long-distance soliton systems and optical time-division multiplexed systems, generates 20-ps-wide transform-limited pulses with a time-bandwidth product of 0.34 at a repetition rate of 8.1 GHz.<<ETX>>

Compact directional coupler switches using quantum well electrorefraction

We have utilized excitonic electrorefraction in reverse‐biased InGaAsP/InP quantum well heterostructures to produce directional coupler switches with active lengths under 600 μm operating at 1.3 and 1.55 μm wavelengths.

Dynamic operation of a three-port, integrated Mach-Zehnder wavelength converter

Wavelength conversion using semiconductor optical amplifiers monolithically integrated in a three-part Mach-Zehnder configuration is achieved for data rates of 1 and 2.5 Gb/s. The three-port configuration allows efficient use of pump signal power, as well as counter-propagation of pump and converted signals, eliminating the need for a filter. Operation of the device at 5 Gb/s in a two-port configuration is also achieved. Dynamic extinction ratios larger than 13 dB, as well as both data-inverting and noninverting operation are demonstrated.<<ETX>>

A 1.54- mu m monolithic semiconductor ring laser: CW and mode-locked operation

The authors have fabricated a monolithic semiconductor ring laser with a diameter of 3.0 mm. A straight tangent waveguide provides two output ports through evanescent coupling. The laser, which exhibits a threshold current of 157 mA, operates in a single longitudinal mode with a linewidth of 900 kHz at a wavelength of 1.54 mu m. The device has been actively mode-locked at the fundamental resonance frequency of 9.0 GHz, yielding 27-ps pulses with a time-bandwidth product of 0.47. Differences in the characteristics of the pulses emitted from the two output ports indicate counterpropagating pulse trains, which because of the mode-locking scheme must collide in the modulated gain section.<<ETX>>