Chao-Kun Lin

High temperature continuous-wave operation of 1.3- and 1.55-/spl mu/m VCSELs with InP/air-gap DBRs

We demonstrate novel electrically pumped 1.3- and 1.55-/spl mu/m vertical cavity surface emitting lasers (VCSELs) with two InP/air-gap distributed Bragg reflectors (DBRs). The active regions comprise conventional InGaAsP multiple quantum wells. A tunnel junction is placed between the active region and the top DBR to convert electrons into holes, thus minimizing the use of p-type material in the structure to reduce the free-carrier loss and achieve current confinement. The whole structure was grown in a single growth run by low-pressure metal-organic chemical vapor deposition (MOCVD). For both 1.3and 1.55-/spl mu/m emission wavelengths, air-gap DBR VCSELs exhibit room-temperature continuous wavelength (CW) threshold current density as low as 1.1 kA/cm/sup 2/, differential quantum efficiency greater than 30%, and CW operation up to 85/spl deg/C. The single-mode output power was 1.6 mW from a 1.3 /spl mu/m VCSEL with a 6.3-/spl mu/m aperture and 1.1 mW from a 1.55 /spl mu/m VCSEL with a 5.7-/spl mu/m aperture under room temperature CW operation.

High-Speed 985 nm Bottom-Emitting VCSEL Arrays for Chip-to-Chip Parallel Optical Interconnects

For chip-scale interconnection, 4 times 12 vertical-cavity surface-emitting laser (VCSEL) arrays have been optimized. Each flip-chip bondable bottom-emitting oxide-confined 985 nm VCSEL have integrated backside lenses, and is capable of modulation at >20 Gb/s with a low current density of only 9.9 kA/cm2. An aggregate data rate of 960 Gb/s was obtained from a chip area of only 1.4 mm times 3.75 mm, or 18.3 Tb/(sldrcm2).

High temperature continuous-wave operation of 1.3-1.55 /spl mu/m VCSELs with InP/air-gap DBRs

High temperature CW operation of electrically pumped 1.3-1.55 /spl mu/m MQW VCSELs using top and bottom InP/air-gap DBRs with record low threshold current density is demonstrated.

Parallel optical interconnect at 10 Gb/s per channel

In many high-end systems, there is a growing need to replace copper interconnects with optical interconnects for link lengths up to 600 meters. 12-channel parallel-optical interconnects with each channel operating at a data rate up to 10 Gb/s are designed, assembled, and demonstrated. This is achieved using bottom-emitting 990-nm VCSELs and bottom-illuminated photodetectors (PDs) flip-chip bonded directly to 12-channel transmitter and receiver integrated circuits, respectively. Results show a 12-channel parallel-optical transmitter module operating at a data rate of 10 Gb/s per channel with all 12 channels operating simultaneously. In addition, a 12-channel parallel-optical receiver module with each channel operating at a data rate up to 10 Gb/s with all channels operating simultaneously is demonstrated. A BER <10/sup -12/ is measured on a single channel operating at a data rate of 10 Gb/s with all 12 channels operating simultaneously after transmission over 100 meters of 50-/spl mu/m core standard multimode ribbon fiber.

MOCVD growth of InGaAsN QWs and 1.3 /spl mu/m VCSELs

This paper demonstrates MOCVD growth of InGaAsN quantum wells and fabrication of vertical cavity surface emitting lasers (VCSELs). Results on the modulation and high temperature characteristics of 1.3 /spl mu/m-range InGaAsN vertical cavity surface emitting lasers (VCSELs) are also presented. Over 1 mW of single-mode output power is obtained at 80/spl deg/C. Clear eye opening at 2.5 Gb/s and 10 Gb/s are obtained up to 120/spl deg/C and 90/spl deg/C, respectively.

Folded-cavity resonators as key elements for optical filtering and low-voltage electroabsorption modulation

Folded-cavity (FC) resonators, which are based on shallow-etched ridge waveguides combined with four deeply etched turning mirrors, are designed and fabricated. The device consists of a resonant FC and a bus waveguide coupled to it through a directional coupler. Optical passive filters, based on this technology, exhibit quality factors in the excess of 5000, with a low insertion loss of 5 dB (including the input coupling loss to a fiber) and more than 15-dB extinction at resonance. When the filter is combined with an electroabsorption active region and is designed to operate in the overcoupled regime, a low-voltage/high-extinction-ratio resonant modulation becomes feasible. The resonant modulator exhibits a low insertion loss (greater than 22-dB extinction at resonance) and offers a low-voltage operation. A change in the applied voltage by 0.7 V (close to the critically coupled conditions) leads to a transmission change of more than 16 dB. Open eye diagrams at 12 Gb/s are presented. To decrease the insertion loss, multiple material bangaps are further monolithically integrated across the wafer by utilizing the quantum-well-intermixing techniques

Self-aligned, buried heterostructure AlInGaAs laser diodesby micro-selective-area epitaxy

We describe the growth and characteristics of AlInGaAs, self-aligned buried heterostructure quantum well lasers deposited by micro-selective-area growth. The lateral waveguide is defined by metalorganic vapor-phase epitaxy in narrow stripe openings; and the natural tendency to form smooth, no-growth {111} sidewall planes produces a low-loss, single-mode waveguide. By proper adjustment of the growth conditions after the waveguide formation, the waveguide may be buried in p-type InP. A buried heterostructure (BH) laser is there formed in a single growth step, eliminating the deterioration associated with air exposure and etch damage, especially for AlInGaAs active regions. The AlInGaAs BH lasers formed in this simple manner exhibit good performance characteristics, with room-temperature threshold current of 4mA.

Long-wavelength VCSELs with InP/air-gap DBRs

We demonstrate novel electrically pumped 1300 nm and 1550 nm VCSELs with two InP/air-gap DBRs. The active regions comprise conventional InGaAsP multiple quantum wells. A tunnel junction is placed between the active region and top DBR to convert electrons into holes, thus minimizing the use of p-type material in the structure to reduce the free-carrier loss and achieve current confinement. The whole structure was grown in a single growth run by low pressure MOCVD. For both 1300 and 1550 nm emission wavelengths, air-gap DBR VCSELs exhibit roomtemperature, CW threshold current density as low as 1.1 kA/cm2, differential quantum efficiency greater than 30%, and CW operation up to 85°C. The single-mode output power was 1.6 mW from a 1300 nm VCSEL with a 6.3 μm aperture; and 1.1 mW from a 1550 nm VCSEL with a 5.7 μm aperture under room temperature CW operation

High-speed 2D VCSEL arrays at 990nm for short reach interconnects

We have demonstrated high density, 2D (4x12) VCSEL arrays operating at an aggregate data rate of over 480Gb/s in an aerial density of 1400x3750 μm2, or 9.14 Tbs/cm2. These flip-chip, bottom-emitting 990nm VCSELs have low drive voltage, low electrical parasitics, improved thermal impedance and 2D scalability over their wire-bonded top emitting counterparts. Excellent high speed performance was obtained through the use of 1) compressively strained InGaAs MQW active region 2) low parasitic capacitance oxide-confined VCSEL structures and 3) low series resistance, high index contrast AlGaAs/GaAs mirrors. 10Gb/s operation was obtained with low operating current density of ~6kA/cm2 at 70C. Our best results to date have achieved data rates greater than 12.5Gb/s @70C at a current density less than 10kA/cm2. The device results show good agreement with theoretically calculated/simulated values. This work was partially supported by DARPA under contract MDA972-03-3-0004.

Demonstration of a low-voltage resonant modulator based on the folded cavity design

A low-voltage folded cavity resonant modulator, based on shallow-etched ridge waveguides combined with four deeply etched turning mirrors is demonstrated. The resonant modulator exhibit a high quality factor in the excess of 5000, low insertion loss, greater than 22 dB extinction at resonance and offers low-voltage operation. A change in the applied voltage by 0.7 V leads to transmission change of more than 16 dB. The DC performance of the modulator is presented