Stress-induced polymer waveguides operating at both 1.31 and 1.55 /spl mu/m wavelengths

Metal-defined polymer optical waveguides have been demonstrated for the first time. A metal strip patterned on top of a polymer slab waveguide causes a stress-induced refractive index change, providing lateral optical mode confinement within the core layer. Fabricated waveguides exhibit low propagation loss values of 1.1 dB/cm at 1.31 /spl mu/m and 1.3 dB/cm at 1.55 /spl mu/m for both TE and TM polarisations.     

High efficiency 90/spl deg/ silica waveguide bend using an air hole photonic crystal region

We propose the hybrid integration of an air hole photonic crystal (PhC) structure with a high /spl Delta/ (0.75%) single-mode silica waveguide to achieve an ultracompact high efficiency 90/spl deg/ bend for transverse-magnetic polarized light. Diffraction from the periodic boundary between the PhC and silica waveguide regions is shown to seriously degrade the optical efficiency of the bend. A microgenetic algorithm (/spl mu/GA) combined with a two-dimensional finite-difference time-domain method is used to modify the PhC and its boundary layer to suppress this diffraction which in turn maximizes bend efficiency. The final optimized structure has a 99.4% bend efficiency at a wavelength of 1.55 /spl mu/m and occupies an area of only 27 /spl times/ 27 /spl mu/m.     

Wideband planar lightwave circuit type variable optical attenuator using phase-generating coupler

A novel wideband planar lightwave circuit type variable optical attenuator (VOA) that incorporates a phase-generating coupler is proposed. The proposed VOA was fabricated on a 1.5%-/spl Delta/ silica-based waveguide, and obtained a low insertion loss of less than 1.2 dB and a low wavelength dependent loss of less than 0.8 dB at attenuation levels of 0 to 25 dB over the C- and L-band wavelength range.     

Isolators, polarizers, and other optical waveguide devices using a resonant-layer effect

This paper investigates the effect of a high-refractive-index layer added onto the clad layer of an optical waveguide. With proper design, the value of the fundamental mode's confinement factor in the added layer can exhibit a resonance. This resonance depends on the added layer's location, thickness, complex index, and wavelength of operation. If loss is incorporated into this added layer, relatively small changes in waveguide properties can result in large changes in loss. This phenomenon is referred to in this paper as the resonant-layer effect (RLE). A number of devices, including isolators, polarizers, and modulators, can be made and/or improved by using the RLE. As examples, this paper describes an integratable isolator giving 240-dB/cm isolation and 13-dB/cm insertion loss, an integratable polarizer with 90-dB/cm rejection and about 0.8-dB/cm insertion loss, and a 300-/spl mu/m-long modulator requiring electric fields of /spl plusmn/5 V//spl mu/m for /spl sim/45% intensity modulation. In general, the resonant layer need not be epitaxial with the waveguide, allowing for integration with a variety of material systems.     

Coupling efficiencies in reflective self-organized lightwave network (R-SOLNET) simulated by the beam propagation method

The reflective self-organized lightwave network (R-SOLNET) enables the formation of self-aligned waveguides in the photorefractive (PR) material between misaligned optical devices by introducing a write beam. The incident write beam from one device and the reflected write beam from the second device induce self-focusing in the PR material and construct a coupling waveguide. A wavelength filter on the waveguide edge is used to facilitate the reflected beam. The beam propagation method reveals that R-SOLNET exhibits higher coupling efficiencies and better tolerances than the one-beam-writing SOLNET and the free-space coupling. The apparent usefulness of R-SOLNET is remarkable for gaps wider than 100 /spl mu/m in 8-/spl mu/m-wide waveguide circuits. For 240-/spl mu/m gap, coupling efficiency better than 50% can be achieved even when the lateral misalignment is as large as 4 /spl mu/m. The results indicate that R-SOLNET may be useful for vertical waveguide constructions of optical z-connections in three-dimensional intrachip optical interconnects and switching systems, as well as for self-aligned optical couplings with devices that cannot emit write beams such as vertical-cavity surface-emitting lasers, photodetectors, and electrooptic switches.     

High-efficiency 1.3 /spl mu/m InAsP-GaInP MQW electroabsorption waveguide modulators for microwave fiber-optic links

High-efficiency electroabsorption waveguide modulators have been designed and fabricated using strain-compensated InAsP-GaInP multiple quantum wells at 1.32-/spl mu/m wavelength. A typical 200-/spl mu/m-long modulator exhibits a fiber-to-fiber optical insertion loss of 9 dB and an optical saturation intensity larger than 10 mW. The 3-dB electrical bandwidth is in excess of 20 GHz with a 50-/spl Omega/ load termination. When used in an analog microwave fiber-optic link without amplification, a RF link efficiency as high as -38 dB is achieved at 10 mW input optical carrier power. These analog link characteristics are the first reported using MQW electroabsorption waveguide modulators at 1.32 /spl mu/m.     

Propagation-mode-controlled fabrication of self-written waveguide in photosensitive polyimide for single-mode operation

We have developed a new fabrication method of single-mode self-written waveguide by controlling the propagation mode in an optical fiber. This method is very appropriate for repeatable fabrication of the single-mode self-written waveguide. Since a Gaussian-like near-field pattern is required for the fabrication of a tiny and uniform waveguide core, the propagation mode in a conventional optical communication fiber was controlled by coupling with an optical fiber having 3-/spl mu/m core, which shows a single-mode operation at visible wavelength region. Single-mode propagation at optical communication wavelength was confirmed for the fabricated self-written waveguide. The evaluated core diameter of the self-written waveguide was /spl sim/9.5 /spl mu/m.     

PCB-compatible optical interconnection using 45/spl deg/-ended connection rods and via-holed waveguides

In this paper, a new architecture for a chip-to-chip optical interconnection system is demonstrated that can be applied in a waveguide-embedded optical printed circuit board (PCB). The experiment used 45/spl deg/-ended optical connection rods as a medium to guide light paths perpendicularly between vertical-cavity surface-emitting lasers (VCSELs), or photodiodes (PDs) and a waveguide. A polymer film of multimode waveguides with cores of 100/spl times/65 /spl mu/m was sandwiched between conventional PCBs. Via holes were made with a diameter of about 140 /spl mu/m by CO/sub 2/-laser drilling through the PCB and the waveguide. Optical connection rods were made of a multimode silica fiber ribbon segment with a core diameter of 62.5 and 100 /spl mu/m. One end of the fiber segment was cut 45/spl deg/ and the other end 90/spl deg/ by a mechanical polishing method. These fiber rods were inserted into the via holes formed in the PCB, adjusting the insertion depth to locate the 45/spl deg/ end of rods near the waveguide cores. From this interconnection system, a total coupling efficiency of about -8 dB was achieved between VCSELs and PDs through connection rods and a 2.5 Gb/s /spl times/ 12-ch data link demonstrated through waveguides with a channel pitch of 250 /spl mu/m in the optical PCB.     

Thermo-optical modulation at /spl lambda/=1.5 /spl mu/m in an /spl alpha/-SiC-/spl alpha/-Si-/spl alpha/-SiC planar guided-wave structure

A planar waveguide based on an amorphous silicon-amorphous silicon carbide heterostructure is proposed for the realization of passive and active optical components at the wavelengths /spl lambda/=1.3-1.5 /spl mu/m. The waveguide has been realized by low temperature plasma enhanced chemical vapor deposition and is compatible with the standard microelectronic technologies. Thermo-optical induced modulation at /spl lambda/=1.5 /spl mu/m is demonstrated in this waveguide. Numerical simulations predict that operation frequencies of about 3 MHz are possible. The measurements have also allowed the determination of the previously unknown thermo-optical coefficient of undoped amorphous silicon at this wavelength.     

Fabrication approach for antiphase narrow linewidth complex coupled 1.55 /spl mu/m DFB lasers

A new method for fabricating narrow linewidth antiphase complex coupled MQW DFB lasers by periodically etching the active layer and quarternary InGaAsP overgrowth is reported. The minimum linewidth for a 375 /spl mu/m long ridge waveguide laser is only 250 kHz at an optical output power of 4 mW.     

Rearrangeable nonblocking SOI waveguide thermooptic 4/spl times/4 switch matrix with low insertion loss and fast response

A rearrangeable nonblocking 4/spl times/4 thermooptic silicon-on-insulator waveguide switch matrix at 1.55-/spl mu/m integrated spot size converters is designed and fabricated for the first time. The insertion losses and polarization-dependent losses of the four channels are less than 10 and 0.8 dB, respectively. The extinction ratios are larger than 20 dB. The response times are 4.6 /spl mu/s for rising edge and 1.9 /spl mu/s for falling edge.     

16 W continuous-wave output power from 100 /spl mu/m-aperture laser with quantum well asymmetric heterostructure

16 W continuous-wave room temperature front facet output optical power and 74% wallplug efficiency were attained in 100 /spl mu/m-aperture 1.06 /spl mu/m-emitting laser diodes with 2-3 mm cavity length. The lasers are based on AlGaAs/GaAs/InGaAs quantum well asymmetric heterostructures with 1.7 /spl mu/m-thick waveguide having 0.34 cm/sup -1/ internal optical loss.     

Low-cost 1.55-/spl mu/m InGaAsP-InP spot size converted (SSC) laser with conventional active layers

We report the realization of a low cost 1.55-/spl mu/m spot size converted (SSC) laser using conventional SCH-MQW active layers. The laser consists of a rectangular gain section, a linear taper and a passive waveguide. The lateral taper and the passive waveguide are fabricated on the same lower SCH layer, using conventional photolithography and RIE (reactive ion etching). The device exhibits low beam divergence of 6.6/spl deg//spl times/10.9/spl deg/ and -2.2-dB coupling loss with a cleaved single-mode fiber. The 1-dB alignment tolerance is /spl plusmn/2.15 /spl mu/m in vertical direction and /spl plusmn/2.3 /spl mu/m in lateral direction, respectively.     

A new integrated optical-mode stripper configuration: Numerical analysis and design

A novel integrated-optical mode stripper configuration is proposed and analyzed numerically by the BPM. Its operation is based on the coupling of all higher order modes into regions with higher refractive index adjacent to the optical waveguide. It is shown that a high transmission of the fundamental mode and a high suppression of higher order modes can be realized at /spl lambda/=1.3 /spl mu/m and /spl lambda/=1.5 /spl mu/m.     

Fabrication and characteristics of GaP-AlGaP tapered waveguide semiconductor Raman amplifiers

We have fabricated GaP-AlGaP tapered waveguide semiconductor Raman amplifiers, and analyzed the effect of tapering in pulse-pumped high-gain operation. The finesse measurement and 80-ps pulse pumped Raman amplification experiment were performed. Although the tapering has caused additional optical loss, the highest gain of 23 dB has been obtained for a tapered waveguide with input facet of 6.0 /spl mu/m/sup 2/ and back facet of 2.9 /spl mu/m/sup 2/ at averaged input power of 170 mW (peak power 26 W). It is shown that the optical loss of the pump light is more severe than the linear optical loss of the signal light when the gain is higher than 20 dB.     

Low-voltage high-speed travelling wave InGaAsP-InP phase modulator

A high-speed low-drive-voltage travelling wave electrodes InGaAsP-InP phase modulator operated at 1.55 /spl mu/m is demonstrated. The modulator is fabricated using a multiple quantum-well optical waveguide with an on chip integrated termination resistor. A small signal bandwidth of 35 GHz and a V/spl pi/ of 1.8 V has been demonstrated.     

Ridged LiNbO/sub 3/ modulators fabricated by a novel oxygen-ion implant/wet-etch technique

This paper demonstrates a new ion implantation and wet-etch technique for fabricating high-quality ridged optical waveguides for high-speed LiNbO/sub 3/-based optical modulators. In addition, the paper demonstrates the fabrication of optical waveguide ridges >3 /spl mu/m in height with 90/spl deg/, and even re-entrant sidewall angles for the first time. The modeling used indicates that 90/spl deg/ (and re-entrant) sidewall ridges can reduce the required modulator drive voltage by 10-20% over modulators with conventional trapezoidal ridge profiles fabricated with reactive ion etching. A 40-Gb/s modulator with a 30-GHz bandwidth, 5.1-V switching voltage at 1 GHz, and a 4.8-dB optical insertion loss is fabricated using the ion implantation/wet-etch process. Fabricated devices showed good stability against accelerated aging, indicating that this process could be used for commercial purposes.     

Design and fabrication of zinc oxide thin-film ridge waveguides on silicon substrate with ultraviolet amplified spontaneous emission

Zinc oxide (ZnO) thin-film ridge waveguides have been designed and fabricated on n-type (100) silicon substrate. A filtered cathodic vacuum arc technique is used to deposit high-crystal-quality ZnO thin films on lattice-mismatched silicon substrates at 230/spl deg/C. A ridge waveguide of width /spl sim/2 /spl mu/m and height /spl sim/0.1 /spl mu/m is defined on the ZnO thin film by plasma etching. Room-temperature amplified spontaneous emission is observed with peak wavelength at /spl sim/385 nm under 355-nm optical excitation. It is found that the net optical gain of the ZnO thin-film ridge waveguides can be as large as 120 cm/sup -1/ at a pump intensity of /spl sim/1.9 MW/cm/sup 2/.     

120/spl deg/C 10-gb/s uncooled direct Modulated 1.3-/spl mu/m AlGaInAs MQW DFB laser diodes

A 1.3-/spl mu/m AlGaInAs multiquantum well ridge waveguide distributed feedback laser diode was developed. By forming n-InGaAsP grating in the n-InP cladding layer close to the active region, accumulation of the holes in the grating layer was reduced and over 5 mW of output power was obtained at 120/spl deg/C. Clear eye opening was confirmed with no mask hits for OC-192 under 10-Gb/s direct modulation at the temperature up to 120/spl deg/C.     

Low-threshold piezoelectric-strained InGaAs-GaAs QW lasers grown on (211)B oriented GaAs substrates

We report the operation of strained layer In/sub 0.20/Ga/sub 0.80/As quantum well lasers grown on (211)B GaAs substrates, thus incorporating a piezoelectric field. Growth was by atmospheric pressure metal-organic vapor phase epitaxy (MOVPE). The threshold current density of a 1000 /spl mu/m/spl times/75 /spl mu/m device is 91 A/spl middot/cm/sup -2/ and waveguide transparency is estimated at 32 A/spl middot/cm/sup -2/ for a simple separate confinement heterostructure (SCH) emitting at 982 nm.