P. De Dobbelaere

Epitaxial lift-off and its applications

In this paper the authors will give an overview of the epitaxial lift-off (ELO) technique and its applications. This first part will describe the basic technology, which includes chemical lift-off, handling bonding, stress, alignment, etc. The second part will give an overview of device results obtained with ELO (LED and lasers on Si, MESFETs on InP, OEICs etc).

Monolithic integration of a spot size transformer with a planar buried heterostructure InGaAsP/InP-laser using the shadow masked growth technique

We present a vertically tapered InGaAsP/InP planar buried heterostructure (PBB) laser for low loss coupling to single-mode fibers. To achieve the vertical tapering we make use of the shadow masked growth technique. Tapered lasers with beam divergences of 15/spl deg/ in both lateral and transverse directions were realized. In comparison with untapered lasers, the coupling losses to cleaved single-mode fibers could be reduced by 4.8 dB down to 5.8 dB.<<ETX>>

GaAs/AlGaAs multiple-quantum-well vertical optical modulators on glass using the epitaxial lift-off technique

A GaAs/Al(0.30)Ga(0.70)As multiple-quantum-well vertical optical modulator has been grown on a GaAs substrate using the metal-organic vapor-phase epitaxy technique. This device was removed from the original substrate and placed on a glass carrier by means of epitaxial lift-off (ELO). Photocurrent measurements before and after the ELO show clear exciton absorption peaks and indicate the development of a Fabry-Perot cavity after ELO due to multiple reflections between the front and back of the ELO film. Transmission measurements show a maximal contrast ratio of 2.9 dB and an insertion loss of 2.8 dB at a wavelength of 831 nm.

Monolithic integration of diffractive lenses with LED-arrays for board-to-board free space optical interconnect

Since optical interconnections can severely reduce problems associated with electrical interconnect technology (including bandwidth limitations, electromagnetic cross talk, signal delay and EMI aspects), the development of suitable electrooptic components is of crucial importance for implementation of optical interconnects in future computer systems. This paper addresses the design, modeling, fabrication as well as experimental assessment of LED-arrays, with diffractive lenses etched into the rear side of the LED-substrate. The suitability of such optical sources for board-to-board optical interconnections will be demonstrated. >

High-density and alignment-tolerant integration of monitoring photodetector arrays onto polymeric guided-wave components

We report on a hybrid integration concept which allows high-density and alignment-tolerant surface mount assembly of top-illuminated photodetector (PD) arrays onto polymeric guided-wave components by means of a micromachined submount with an integrated mirror. This research aims at the development of polymeric waveguide based devices with an embedded optical power monitoring capability for applications in optical fiber communication networks. A prototype integrated multichannel optical power monitor comprising an eight-channel PD module and a polymeric waveguide splitter array was demonstrated which exhibited an average insertion loss of 5.2 dB, a PD coupling efficiency of -2.6 dB, and a crosstalk value of -17.1 dB between adjacent channels. Low polarization and wavelength sensitivity (/spl sigma/<0.1 dB) was confirmed over a spectral range of 40 nm in both telecom wavelength windows.

Compact multichannel in-line power monitor

We report a pigtailed compact eight-channel in-line optical power monitor module based on a polymeric waveguide splitter array with a surface mounted photodetector (PD) chip. This prototype device comprised 50/50 power splitters and exhibited an average fiber-to-fiber insertion loss of 5.2 dB at 1310 nm and 5.3 dB at 1550 nm. An average PD coupling efficiency of -2.6 dB and crosstalk of -17.1 dB to adjacent channels was observed. We confirmed low variation of these values (standard deviation /spl sigma/<0.1 dB) in the 1290-1330 nm and 1525-1565 nm optical windows and over an input power range of 12 dB.

Advanced Structures For Integrated Optics Realized With Shadow Masked Growth

The fabrication of integrated optic devices in semiconductor materials requires advanced processing techniques. In this paper, we propose the shadow masked growth (SMG) as an alternative to other techniques such as multi-step etching, mass transport, selective growth, shadow masked etching, etc. Two applications will be described: refractive lenses and tapered structures. The lenses can easily be integrated with LEDs or vertical cavity substrate-emitting laser diodes, or can be used for the realisation of 3-D microcavities. The tapered structures find interesting applications in optical mode shape transformers (e.g. for improved waveguide fibre coupling) and in bandgap engineering (when using quantum wells).

First polymeric splitter array with integrated PD-chip for multichannel power monitoring

We report the first 8-channel power monitor based on a polymeric splitter array with surface mounted PD-chip. Combination with polymeric thermo optical (TO) switch technology will readily enable development of compact automatic channel power equalisers and protection switches.

Cost-effective and high-density integration of monitoring photodetector arrays onto polymeric guided-wave components

We report on a hybrid coupling concept which allows high-density integration of top illuminated photodetector arrays with polymeric guided-wave based optical network components by means of a micromachined submount with an integrated mirror. The etching of a complementary alignment structure into the polymeric layer stack allows passive assembly with a 1.0 dB alignment tolerance range of about 40 /spl mu/m. A prototype 8-channel detector module integrated with a straight single mode polymeric waveguide array exhibited a coupling efficiency of about -7.7 dB and an average crosstalk value of -21.3 dB between adjacent channels at 1300 nm.

Integrating optical receiver transplanted by epitaxial lift off

A GaAs integrating optical receiver has been designed and realized using a commercial foundry process. The receiver was then transplanted by epitaxial lift off (ELO) onto an InP substrate. This technology allows the monolithical integration of previously incompatible materials onto one chip. To our knowledge the chip described is the most complex chip that has been transplanted by ELO. The integrating receiver described here presents a novel circuit topology to integrate optical input power.