The International Symposium on Blue Lasers & LEDs

AbstractThis was the third time that the II–VI and III–V blue emitting device communities had been brought together in one meeting (following meetings in California and Trieste). The aim was to provide a forum bringing together experts from both research fields in an attempt to solve common problems which block the realisation of commercially available blue LD's. With the announcement of the first GaN-based blue LD in January 96, and Sony's 100hr laser ZnMgSSe blue LD shortly after, the timing for this Symposium could not have been better. This was reflected by the fact that it was over-subscribed by nearly 100%, a modest meeting planned for about 200 turned into a major conference for nearly 500 in the last few weeks of planning

InGaN/GaN Laser Diodes with High Order Notched Gratings

We report on InGaN/GaN distributed feedback laser diodes with high order gratings emitting at a single wavelength around 428 nm. The 39th order notched gratings have the advantage of a simplified fabrication route with no need for overgrowth. The laser ridge and grating were formed by electron beam lithography followed by ICP etching. The as-cleaved lasers emitted in the pulsed regime with a peak single-mode output power of 15 mW. Optimization of the grating design should lead to higher power single wavelength operation

Experimental Demonstration of 38 Gbps over 2.5 m OWC Systems with Eye-safe 850 nm SM-VCSELs

With a directly modulated 850 nm single-modevertical cavity surface emitting laser (SM-VCSEL), we experimentally achieve a gross data rate of ∼38 Gbps over a 2.5 moptical wireless communication (OWC) link at the 7% ReedSolomon forward error correction (RS-FEC) limit. The OWClink is demonstrated using an eye-safe transmitted optical powerof -1.47 dBm and discrete multi-tone (DMT) modulation withadaptive bit-and-power loading. The SM-VCSEL has a relativeintensity noise (RIN) of ∼-137 dB/Hz, which is lower than that ofa typical commercial 850 nm multimode VCSEL (∼-129 dB/Hz).Therefore, under almost identical OWC link operating conditions, the SM-VCSEL provides a gross data-rate increase of∼19 Gbps and an optical signal-to-noise-ratio (SNR) gain of∼5 dB compared to its multimode counterpart having a similarmodulation bandwidth. Furthermore, we demonstrate an errorfree net data rate of ∼17 Gbps at a received optical power of-7 dBm, which suggests the feasibility of utilising the SM-VCSELto realise indoor gigabit OWC applications

Correlation between p-GaN growth environment with electrical and optical properties of blue LEDs

Two blue (450 nm) light–emitting diodes (LED), which only differ in top p-GaN layer growth conditions, were comparatively investigated. I-V, C-V, TLM, Electroluminescence (EL) and Photoluminescence (PL) techniques were applied to clarify a correlation between MOCVD carrier gas and internal properties. The A-structure grown in the pure N2 environment demonstrated better parameters than the B-structure grown in the N2/H2 (1:1) gas mixture. The mixed growth atmosphere leaded to an increase of sheet resistances of p-GaN layer. EL and PL measurements confirmed the advantage of the pure N2 utilization, and C(VR) measurement pointed the increase of static charge concentration near the p-GaN interface in the B structure

Experimental demonstration of 38 Gbps over 2.5 m OWC systems with eye-safe 850 nm SM-VCSELs

With a directly modulated 850 nm single-mode vertical cavity surface emitting laser (SM-VCSEL), we experimentally achieve a gross data rate of ∼38 Gbps over a 2.5 m optical wireless communication (OWC) link at the 7% Reed-Solomon forward error correction (RS-FEC) limit. The OWC link is demonstrated using an eye-safe transmitted optical power of -1.47 dBm and discrete multi-tone (DMT) modulation with adaptive bit-and-power loading. The SM-VCSEL has a relative intensity noise (RIN) of ∼-137 dB/Hz, which is lower than that of a typical commercial 850 nm multimode VCSEL (∼-129 dB/Hz). Therefore, under almost identical OWC link operating conditions, the SM-VCSEL provides a gross data-rate increase of ∼19 Gbps and an optical signal-to-noise-ratio (SNR) gain of ∼5 dB compared to its multimode counterpart having a similar modulation bandwidth. Furthermore, we demonstrate an error-free net data rate of ∼17 Gbps at a received optical power of -7 dBm, which suggests the feasibility of utilising the SM-VCSEL to realise indoor gigabit OWC applications

Adaptive optical interconnects: The ADDAPT project

Existing optical networks are driven by dynamic user and application demands but operate statically at their maximum performance. Thus, optical links do not offer much adaptability and are not very energy-effcient. In this paper a novel approach of implementing performance and power adaptivity from system down to optical device, electrical circuit and transistor level is proposed. Depending on the actual data load, the number of activated link paths and individual device parameters like bandwidth, clock rate, modulation format and gain are adapted to enable lowering the components supply power. This enables exible energy-efficient optical transmission links which pave the way for massive reductions of CO2 emission and operating costs in data center and high performance computing applications. Within the FP7 research project Adaptive Data and Power Aware Transceivers for Optical Communications (ADDAPT) dynamic high-speed energy-efficent transceiver subsystems are developed for short-range optical interconnects taking up new adaptive technologies and methods. The research of eight partners from industry, research and education spanning seven European countries includes the investigation of several adaptive control types and algorithms, the development of a full transceiver system, the design and fabrication of optical components and integrated circuits as well as the development of high-speed, low-loss packaging solutions. This paper describes and discusses the idea of ADDAPT and provides an overview about the latest research results in this field

VCSEL quick fabrication of 894.6 nm wavelength epi‐material for miniature atomic clock applications

A vertical cavity surface emitting laser (VCSEL) quick fabrication (VQF) process is applied to epitaxial materials designed for miniature atomic clock applications (MACs). The process is used to assess material quality and uniformity of a full 100 mm (4‐inch) wafer against the stringent target specification of VCSELs for MACs. Target specifications in optical power (>0.6 mW) and differential efficiencies (<0.5 W/A) are achieved over large portions of a wafer; however, the variation in the oxide aperture diameter is shown to limit the yield. The emission of the fundamental mode at 894.6 nm at 70 ℃ ${}^{\circ}\mathrm{C}$ is met over a significant area of the wafer for ∼4 μ $\mu$ m aperture multi‐mode devices. The consideration of the on‐wafer variation reveals that further optimisation is required to increase the device yield to levels required for volume manufacture

Gain measurements on vertical cavity surface emitting laser material using segmented contact technique

We report direct measurements of the optical gain profile for a vertical cavity surface emitting laser (VCSEL) epitaxial structure, by characterising the transverse electric (TE) in-plane net modal gain using the segmented contact method

II-VI blue emitting lasers and VCSELs

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International conference on II-VI compounds &amp; devices

AbstractAn atmosphere of anticipation resided at the opening session of this, the seventh international II–VI conference. Over the past two years since the last meeting at Newport, Rhode Island, the onlyheadline news in the II–VI community was the slow but a relentless increase in the lifetimes of blue emitting laser diodes. Delegates attending the device sessions expected something spectacular, since all the major players, Sony, Phillips, 3M and Brown-Purdue had something to say. From very early on in the conference the message was clear; there are no shortcuts in the development of these devices. The problems hinted at four years ago, and highlighted two years ago, are still with us, the community just has a greater insight into them now. Overall, however, the underlying feel of this meeting was of diversification and expansion of the range of research undertaken in the II–VI field, along with a more concentrated effort on the problems specific to lasers and LEDs