J.J. Hindi

High single mode operation from hybrid ion implanted/selectively oxidized VCSELs

The modal discrimination can be augmented by creating a central region of gain surrounded by a region of optical loss. We report single mode output of more than 5 mW for 850 nm VCSELs fabricated using a hybrid ion implantation and selective oxidation device structure designed to achieve this end.

Lithographically-defined gain apertures within selectively oxidized VCSELs

Summary form only given.Selectively oxidized vertical cavity surface emitting lasers (VCSELs) have demonstrated record performance such as low threshold current/voltage, high efficiency, and high-speed modulation characteristics. Because of the strong index confinement created by buried oxide layers used to define the laser cavity, oxidized VCSELs typically operate in multiple transverse optical modes, whereas single-mode operation is required for many VCSEL applications. One approach to discriminate against higher-order optical modes is to define a small gain region within a larger diameter cavity. We report on high-performance gain-apertured selectively oxidized VCSELs, which exhibit high single-mode operation as high as 3 m with side mode suppression ratios>30 dB.

Comparison of fabrication approaches for selectively oxidized VCSEL arrays

The impressive performance improvements of laterally oxidized VCSELs come at the expense of increased fabrication complexity for 2-dimensional arrays. Since the epitaxial layers to be wet-thermally oxidized must be exposed, non-planarity can be an issue. This is particularly important in that electrical contact to both the anode and cathode of the diode must be brought out to a package. We have investigated four fabrication sequences suitable for the fabrication of 2- dimensional VCSEL arrays. These techniques include: mesa etched polymer planarized, mesa etched bridge contacted, mesa etched oxide isolated (where the electrical trace is isolated from the substrate during the oxidation) and oxide/implant isolation (oxidation through small via holes) all of which result in VCSELs with outstanding performance. The suitability of these processes for manufacturing are assessed relative to oxidation uniformity, device capacitance, and structural ruggedness for packaging.

Single transverse mode selectively oxidized vertical cavity lasers

Vertical cavity surface emitting lasers (VCSELs) which operate in multiple transverse optical modes have been rapidly adopted into present data communication applications which rely on multi-mode optical fiber. However, operation only in the fundamental mode is required for free space interconnects and numerous other emerging VCSEL applications. Two device design strategies for obtaining single mode lasing in VCSELs based on mode selective loss or mode selective gain are reviewed and compared. Mode discrimination is attained with the use of a thick tapered oxide aperture positioned at a longitudinal field null. Mode selective gain is achieved by defining a gain aperture within the VCSEL active region to preferentially support the fundamental mode. VCSELs which exhibit greater than 3 mW of single mode output power at 850 nm with mode suppression ratio greater than 30 dB are reported.

Two-dimensional 8/spl times/8 photoreceiver array and VCSEL drivers for high-throughput optical data links

Two custom GaAs integrated circuits (ICs) have been developed for enabling vertical cavity surface emitting laser (VCSEL) arrays to be used for high throughput spatial division multiplexed (SDM) optical data links. A 16-channel driver IC was developed to drive the VCSEL array and an 8/spl times/8 monolithic photoreceiver, which spatially matches the VCSEL array, was developed for receive. Both of these circuits were fabricated in a standard commercial GaAs MESFET process with parasitic photodetectors used for the photoreceivers. Power dissipation and circuit size were primary design challenges for both circuits. The present 8/spl times/8 array size along with an estimated usable channel speed of 1 Gb/s allows for an aggregate throughput of 64 Gb/s.

Monolithically integrated VCSELs and photodetectors for microsystem applications

Summary form only given. We have fabricated integrated resonated cavity photodetectors with selectively oxidized VCSELs by etching away a portion of the top distributed Bragg reflector mirror of nominally 850 nm VCSEL lasers.

Improved performance of selectively oxidized visible VCSELs

The recent development of infra-red selectively oxidized vertical cavity surface emitting lasers (VCSELs) has been enabled through improvement of the oxide aperture design within the laser cavity. VCSEL designs using thin oxide apertures offset a few periods away from the optical cavity have been demonstrated to reduce optical confinement and loss. 650 nm and shorter wavelengths are important for optical scanning applications and low cost optical interconnects based on plastic optical fiber (POF). For example POF has minimum attenuation at 650 nm, indicating that visible VCSELs are appropriate for the development of gigabit/sec low cost optical data links. We report the improved performance of selectively oxidized visible VCSELs which employ a single thin offset oxide aperture.

High-power single mode operation of hybrid ion-implanted/selectively-oxidized VCSELs

We first present numerical simulations that quantify this approach by predicting lateral mode discrimination for different sized gain apertures. These calculations are experimentally confirmed by the fabrication and testing of 850 nm VCSELs employing hybrid ion implantation/selective oxidation that produce a single-mode output of more than 5 mW. We performed VCSEL simulations using a 2D axisymmetric finite-difference code that solves for cavity eigenmodes including both mode shape and energy loss rate for a realistic VCSEL structure that includes gain and loss in the quantum well(s). We chose a VCSEL comprised of a 1-/spl Lambda/ cavity containing a single 100 A quantum well with 34 DBR pairs.

Final Report on LDRD Project: Heterogeneous Integration of Optoelectronic Arrays and Microelectronics

Integrated microsystems provide the benefits of small size, low power consumption, robustness, and potentially inexpensive manufacture. However, multifunctional advanced microsystems often require a combination of microelectronic and photonic technologies, For example, high-density 2-dimensional integrated optoelectronic arrays are the basic components necessary to construct real-time electro-optical signal processing and analog information processing microsystems. In corresponding *no longer at Sandia **L&M Technologies, Inc.

Flip-chip integration of selectively oxidized 850 nm VCSEL arrays

Summary form only given. We report the fabrication techniques for flip-chip integration of selectively oxidized 850 nm 8x8 individually addressable VCSEL arrays. For robust integration of 2-dimensional 850 nm VCSEL arrays to microelectronics, there are three challenges to overcome: 1) reliable bonding; 2) mechanically stable packaging; and 3) through substrate light emission.