A general formula is given that expresses frequency chirping in some types of external intensity modulators, such as the loss modulator, directional-coupler-type modulator, Mach-Zehnder interferometry-type modulator, and total-internal-reflection-type modulator. The chirping phenomenon treated is caused by the phase modulation due to an accompanied refractive index change. It is uniquely expressed in terms of an alpha -parameter that contributes to frequency chirping in the same manner as in the direct modulation of a semiconductor laser. In addition, the transmission bandwidth of a single-mode fiber system using an external modulator is discussed and compared with the results obtained utilizing direct laser modulation. >

Frequency chirping in external modulators

Semiconductor photonic integrated circuits (PICs) refer to that subset of optoelectronic integrated circuits (OEICs) which focus primarily on the monolithic integration of optically interconnected guided-wave optoelectronic devices. The principal motivation for PIC research is the expected cost reduction and packaging robustness associated with replacing individually aligned, single-mode optical connections between discrete optoelectronic devices with lithographically produced integrated waveguides. This field has recently seen significant advances resulting from improved III-V epitaxial crystal growth and related processing techniques. A discussion is presented of the design and fabrication issues, illustrated by a number of recently demonstrated InP-based PICs. >

Semiconductor photonic integrated circuits

A description is given of a GaAs-AlGaAs, loaded-line traveling-wave modulator which has achieved bandwidths up to 36 GHz to date with low ( >

High-speed III-V semiconductor intensity modulators

Because the electroabsorption effect in semiconductor multiple quantum well material is approximately 50 times larger than in bulk semiconductors, significant interest has been generated in the use of MQW's in optical modulators Small high-speed devices have been made which show promise for external modulators in optical transmission systems, as well as for encoding and processing components in optical interconnect and signal processing systems The fact that these modulators are made from III-V semiconductors had led to interest in integration of these components with other active optoelectronic components Although most devices have operated with light of a wavelength of 085 mu m, recently much progress has been made in applying this technology to devices operating near 155 mu m The author reviews the work of the last few years in this field and indicates some future directions >

Multiple quantum well (MQW) waveguide modulators

Integrated OpticsIntegrated Optics and Optical SwitchingIntegrated Optics: Theory and TechnologyIntroduction to Integrated OpticsElements of Photonics, Volume IIEncyclopedic Handbook of Integrated OpticsOptical Fiber Communication Conference and Sixth International Conference on Integrated Optics and Optical Fiber CommunicationIntegrated Optical Circuits and ComponentsIntegrated OpticsAdvances in Integrated OpticsFundamentals of Fibre Optics in Telecommunication and Sensor SystemsIntegrated OpticsIntegrated Optics, Microstructures, and SensorsMulti-Photon Quantum Information Science and Technology in Integrated OpticsIntegrated Optics, Microstructures, and SensorsIntegrated PhotonicsOptics and LasersA Consideration of Possibilities and Difficulties in Passive Circuits in Integrated OpticsSemiconductor Integrated Optics for Switching LightIntegrated OpticsIntegrated OpticsAdvanced Materials for Integrated Optical WaveguidesIntroduction to Semiconductor Integrated OpticsCommercial Integrated OpticsIntegrated OpticsIntegrated Optics and MicrostructuresElectromagnetic Principles of Integrated OpticsIntegrated Optics and Micro-Optics with PolymersIntroduction to Integrated OpticsIntegrated Optics SuppliersIntegrated Optics: Theory and TechnologyDiffractive Optics and Optical MicrosystemsIntegrated Optics and OptoelectronicsFiber and Integrated OpticsEncyclopedic Handbook of Integrated OpticsFirst International Conference on Integrated Optical Circuit EngineeringIntegrated OpticsIon Exchange in Single Crystals for Integrated Optics and OptoelectronicsOptics and LasersIntegrated Optics: Devices, Materials, and Technologies

http://ieeexplore.ieee.org/iel5/3/23092/01072971.pdf

Integrated optics

Monolithic integration of a 1.55-μm InGaAsP/InP distributed feedback (DFB) laser and an electroabsorption (EA) modulator was studied. The difference between the lasing photon energy and the bandgap energy of the modulator waveguide was designed to be 30-40 meV, taking into account the linewidth-enhancement factor and the zero-bias absorption loss. The integrated devices were grown by three-step vapor phase epitaxy (VPE). The CW threshold current at 20°C of the DFB laser part with a buried heterostructure was 30-60 mA and the breakdown voltage of the modulator part with a strip-loaded stripe geometry was 20-40 V, and these values indicated satisfactory crystal quality in the VPE epitaxial layers. The operating voltage of the modulator to give on:off ratios of 10:1 and 100:1 was 1.5- 4 V and 2.5-6.5 V, respectively, depending on the length in the range 200-500 \mu m. A 3-dB bandwidth of about 2.5 GHz and a linewidth-enhancement factor of about 1.6 were obtained for the integrated modulator.

Monolithic integration of InGaAsP/InP distributed feedback laser and electroabsorption modulator by vapor phase epitaxy

We describe fabrication and characterization of an electroabsorption (EA) light modulator (LM) with a strip-loaded GaInAsP planar waveguide. The EA LM's were fabricated from hydride vapor-phase-epitaxy (VPE) grown wafers. The electroabsorption, the insertion loss, the electrical properties, and the modulation characteristics were investigated for the EA LM's. The drive voltage at a 99-percent modulation depth has been noticeably reduced to 4.5 V by optimizing the thicknesses of the epitaxial layers. The total capacitance of 1.5 pF was obtained by inserting an insulating film under the wire-bonding pad and by improving the mount design. Consequently, a 3-dB bandwidth of 3.8 GHz has been achieved and a pulse modulation operation under 2 Gbit/s nonreturn-to-zero (NRZ) pseudorandom pattern has also been confirmed. Moreover, the dynamic spectra of the EA modulators were measured for the first time. A spectral broadening factor α has been determined to be 1-4 from a relative strength of the sideband to the carrier and it has been experimentally found to decrease with increasing the electric field inside the absorptive waveguide. As the other measures of merit for the EA LM's, the extinction ratio over 23 dB and the insertion loss of 10-14 dB including a coupling loss due to an end-fire method were obtained. As a whole, these results have exhibited that the EA LM is a promising external modulator which will be monolithically integrated into a gigabit per second optical source with a dynamic single-mode laser.

Y. Noda

Papers

Monolithic integration of InGaAsP/InP distributed feedback laser and electroabsorption modulator by vapor phase epitaxy

High-speed electroabsorption modulator with strip-loaded GaInAsP planar waveguide