J.B.D. Soole

Monolithic InP/InGaAsP/InP Grating Spectrometer for the 1.48-1.56 μm Wavelength Range

We report a two‐dimensional grating spectrometer implemented in an InP/InGaAsP/InP planar waveguide for use in the low‐loss 1.5 μm wavelength fiber band. The spectrometer uses a single vertical‐walled focusing reflection grating to disperse 78 channels, spaced at 1 nm intervals, with diffraction‐limited resolution (∼0.3 nm) and a high channel isolation (≳19 dB). The spectrometer may be used such that it is insensitive to the state of the input polarization.

Use of multimode interference couplers to broaden the passband of wavelength-dispersive integrated WDM filters

We describe how multimode interference couplers (MMI) may be used to broaden and flatten the passband of integrated wavelength-dispersive filters. We discuss the approach and demonstrate its effectiveness with a passband-broadened InP arrayed waveguide filter operating at 1.5 /spl mu/m.

Ultracompact monolithic integration of balanced, polarization diversity photodetectors for coherent lightwave receivers

The authors have monolithically integrated an optical front-end on InP for balanced, polarization-diversity coherent lightwave reception which is only 1.3-mm long. Low on-chip insertion loss (<4.5 dB) and balanced photoresponse (1.05:1 or better) are achieved at 1.5- mu m wavelength using straightforward, regrowth-free fabrication. Low-capacitance photodetectors (<or=0.15 pF) are employed for high bandwidth operation.<<ETX>>

Simultaneous Multiple Wavelength Operation of a Multistripe Array Grating Integrated Cavity Laser

Simultaneous multiple‐wavelength operation of a multistripe array grating integrated cavity laser is reported. We demonstrate simultaneous lasing from a single output port at 2, 3, and 4 discrete wavelengths, each independently selected from a comb of 9 wavelengths set at ∼2 nm intervals, from 1512 to 1528 nm. Signal cross talk is examined for the case of two‐wavelength emission and found to be independent of the wavelength separation. The emission wavelengths were linearly spaced to within ±0.02 nm, while the comb’s central wavelength deviated by less than 2 nm from its design value. This is the highest wavelength linearity and accuracy so far recorded for a monolithic multiwavelength source.

Wavelength‐selectable laser emission from a multistripe array grating integrated cavity laser

We report laser operation of a multistripe array grating integrated cavity (MAGIC) laser in which the wavelength of the emission from a single output stripe is chosen by selectively injection pumping a second stripe. We demonstrate a device that lases in the 1.5 μm fiber band at 15 wavelengths, evenly spaced by ∼2 nm. The single‐output/wavelength‐selectable operation, together with the accurate predefinition of the lasing wavelengths, makes the MAGIC laser a very attractive candidate for use in multiwavelength networks.

High-speed performance of OMCVD grown InAlAs/InGaAs MSM photodetectors at 1.5 mu m and 1.3 mu m wavelengths

A report is presented on the fabrication of high-speed In/sub 0.53/Ga/sub 0.47/As metal-semiconductor-metal (MSM) photodetectors incorporating a high-quality lattice-matched InAlAs barrier enhancement layer, grown by organometallic chemical vapor deposition (OMCVD). Fast responses of approximately 55 ps full-width half-maximum at 1.5 mu m and approximately 48 ps at 1.3 mu m wavelengths are observed, corresponding to intrinsic device bandwidths of approximately 8 GHz and approximately 11 GHz, respectively. The absence of any tail to the pulse response, and of any low-bias DC gain, indicates a low-trap density at the InAlAs/InGaAs heterointerface. Bias independent dark currents of 10-20 mu A are observed below breakdown, which occurred at >30 V in devices with a 500-A-thick InAlAs layer.<<ETX>>

Efficient vertical coupling of photodiodes to InGaAsP rib waveguides

We demonstrate vertical integration of InGaAs mesa photodiodes with InGaAsP rib waveguides employing an intermediate optical impedance matching layer. The diode length necessary for 90% light absorption at 1.52 μm wavelength was 42 μm, a threefold reduction in diode length with respect to previous work employing similar waveguides without a matching layer. The quantum efficiency was observed to be almost independent of the optical wavelength and polarization. The influence of spatial transient intensity redistribution effects on these devices is investigated in detail.

High-frequency performance of InGaAs metal-semiconductor-metal photodetectors at 1.55 and 1.3 μm wavelengths

The high‐speed performance of InGaAs interdigitated metal‐semiconductor‐metal (M‐S‐M) photodetectors illuminated with 1.55 and 1.3 μm wavelength radiation is modeled using a two‐dimensional transit time calculation. Excellent agreement is found with the experimental pulse response of detectors with interdigital spacings of 2 and 3 μm. We study the dependence of the bandwidth on the device dimensions, and also examine the quantum efficiency. The results should aid the design of InGaAs M‐S‐M detectors with the optimum combination of bandwidth and efficiency for a given application.

Fast high‐efficiency integrated waveguide photodetectors using novel hybrid vertical/butt coupling geometry

We report a novel coupling geometry for integrated waveguide photodetectors−a hybrid vertical coupling/butt coupling scheme that allows the integration of fast, efficient, photodetectors with conventional double heterostructure waveguides. It can be employed to yield a planar, or pseudo‐planar, surface that supports further levels of integration. The approach is demonstrated with a 25‐μm‐long p‐i‐n detector integrated with an InP/InGaAsP/InP waveguide, which displays a high (∼90%) efficiency and large (∼15 GHz) bandwidth. This is the fastest high‐efficiency integrated waveguide photodetector reported to date.

Efficient InGaAsP/InP multiple quantum well waveguide optical phase modulator

We report an InGaAsP/InP multiple quantum well optical phase modulator which has a high phase modulation efficiency and low loss modulation over the entire 1.5–1.56 μm fiber band. For a 4‐mm‐long device, π phase modulation requires a modulation voltage of only 0.6 V at 1.49 μm and 1.1 V at 1.55 μm wavelength. The absorption modulation for a 0–5 V bias change is negligible at 1.55 μm, rising to 0.7 cm−1 at 1.49 μm. The spectral dependence of the electrorefraction from the quantum‐confined Stark effect has also been measured for the first time over a wide continuous wavelength range. Far from the absorption edge the electrorefraction decreases approximately as the square of the energy detuning.