R. van Roijen

Compact InP‐based ring lasers employing multimode interference couplers and combiners

Multimode interference (MMI) 3 dB couplers and MMI power combiners have been integrated with compact InP/InGaAsP ring lasers (R=150 μm). Radiative loss from the curves is small, and MMI 3 dB couplers are shown to be more efficient than conventional Y junctions. In addition, we demonstrate improved efficiency by combining counterpropagating beams in a single output by means of a MMI combiner. Single mode spectral behavior, with 35 dB side mode suppression, has been measured and is explained as resulting from coupled cavities.

Reflection properties of multimode interference devices

We report on the reflection properties of multimode interference (MMI) devices: we distinguish between reflection back into the input waveguides and internal resonance modes due to the occurrence of simultaneous self-images. Because of self-imaging, reflection can be extremely efficient, even in the case of MMI devices with optimized transmission. This conclusion is confirmed by the observed spectral behavior of InP-based ring lasers incorporating MMI 3 dB couplers and MMI power splitters. Several techniques are proposed to minimize the influence of these reflections.<<ETX>>

Surface analysis of reactive ion‐etched InP

A dry‐etch process for InP is developed using a mixture of Cl2, Ar, CH4, and H2. This process results in a high etch rate and good anisotropy. The induced damage is investigated by surface characterization after etching, using x‐ray photoelectron spectroscopy, Rutherford backscattering spectrometry, photoluminescence measurements, and transmission electron microscopy. The etch mechanism is briefly discussed.

Over 15 dB gain from a monolithically integrated optical switch with an amplifier

An optical switch is monolithically integrated with a semiconductor optical amplifier on a InP substrate. The switch is of the total internal reflection type. The device has achieved 15-dB chip gain at 1530-nm wavelength and fiber-to-fiber lossless transmission over a wavelength range of 80 nm. Crosstalk attenuation varies from 13 to 6 dB. This device demonstrates the feasibility of lossless integrated optics on InP. The technology applied allows monolithic integration of various active components with a minimum of extra technology steps.<<ETX>>

Sub‐mA threshold operation of λ=1.5 μm strained InGaAs multiple quantum well lasers grown on (311)B InP substrates

1.5 μm wavelength InxGa1−xAs‐InGaAsP (x=0.7, resulting in 1.2% compressive strain and x=0.53, resulting in zero strain) multiple quantum well (MQW) structures were grown on (311)B, (511)A, (511)B, and (001)InP substrates by low‐pressure organometallic vapor phase epitaxy (LP‐OMVPE). Intense and narrow linewidth room‐temperature photoluminescence spectra indicate the device quality of the MQW structures. Strained MQW lasers grown on InP substrates misoriented towards (111)B show about 25% lower threshold current densities than the unstrained MQW lasers. The high quality of the strained MQW structures grown on (311)B InP substrates is demonstrated by the realization of 0.9 mA threshold current buried heterostructure lasers employing semi‐insulating current blocking layers, and entirely grown by LP‐OMVPE.

Ultracompact multimode interference waveguide devices

Coupling, branching and routing devices are key components for photonic integrated circuits. This paper discusses multimode interference and self-imaging and shows how this effect has created a new class of low-loss, ultracompact and fabrication tolerant routing devices.<<ETX>>

Large Bandwidth Polarisation Independent and Compact 8 Channel PHASAR Demultiplexer/Filter

The first broadband polarisation independent Phasar based demultiplexer/filter is demonstrated employing non-birefringent InGaAsP(λg = 0.97 μm)-on-InP raised strip waveguides. The device exhibits a channel spacing of 2 nm, on-chip loss of 4-5 dB, a cross talk better than -25 dB and a 3 dB channel bandwidth of 0.9 nm. The Phasar size is 2.6×2.3 mm2. The fibre-chip-coupling loss is less than 1 dB.

Improved device ruggedness by floating buffer ring

An integrated low-substrate-leakage diode structure is considered, operated in reverse breakdown mode, having a parasitic npn transistor. At high current, the Kirk effect, causing shift of the potential by the space charge of moving carriers, leads to high electric fields and causes device degradation. The application of a protective n+ buffer ring around the cathode redistributes field and current and improves the ruggedness. This principle is also successfully applied for improved ESD performance of a lateral DMOST in a Silicon-on-Insulator process.

Single-mode monolithic ring laser with verlical grating coupler

membrane mirror are shown in Figs. 2 and 3. Figure 2 shows the initial shape of the reflecting surface, while Fig. 3 corresponds to a mirror, which is deflected electrostatically by 1.2 pm. The surface profiles have been reconstructed from the fringe patterns using the fast Fourier transform alg~rithm.~ For the initial pattern shown in Fig. 2, the peak to peak and mean square deviations have been established as 6 = 0.8A and U = 0.13X correspondently. Extraction of the initial wafer astigmatism reduces these values to 6 = 0.4A and U = A/16. To check the yield strength, the flexible mirror has been repeatedly deformed by an external pressure to a deflection amplitude of 50 pm. After removal of the load, membrane elastically went back to its initial shape with no traces of residual deformation. Optically plane aluminum coated flexible mirror have been integrated into Si chip. The fabrication procedure is compatible with silicon IC processing. Initial optical quality of mirror satisfies the standard demands to reflecting optics. Adaptive mirror with 10 mm by 10 mm reflecting surface, controlled by array of electrostatic actuators is available in a 30 mm by 30 mm IC house. Author is grateful to Prof. Dr. S. Middlehoek, head of the Laboratory of Electronics Instrumentation, Delft University of Technology, for stimulating discussions and support and to Dr. Lina Sarro from DIMES for IC processing.

Sub-mA threshold operation of lambda =1.5 mu m strained InGaAs multiple quantum well lasers grown on

1.5- mu m wavelength In/sub x/Ga/sub 1-x/As/InGaAsP (x=0.7, resulting in 1.2% compressive strain and x=0.53, resulting in zero strain) multiple quantum well (MQW) structures were grown on