Error‐free 46 Gbit/s operation of oxide‐confined 980 nm VCSELs at 85°C

Abstract

A new design of oxide-confined 980 nm vertical-cavity surface-emitting lasers (VCSELs) particularly well-suited for very-short-reach (∼2 m and shorter) optical interconnects is presented. A new record for temperature-stable high bit rate VCSELs is achieved. Error-free data transmission at 46 Gbit/s is achieved up to a record-high temperature of 85°C. The maximum bit rate and −3 dB bandwidth at room temperature are 50 Gbit/s and 24.7 GHz, respectively.Introduction: Vertical-cavity surface-emitting lasers (VCSELs) for very-short-reach (VSR, ∼2 m and shorter) optical interconnects in data centre switches, supercomputers and for on-chip integrated photonics must operate with high energy efficiency at large bit rates to viably replace copper-based interconnects. In addition, uncooled hightemperature (85°C) operation, low heat dissipation and the ability to be integrated with silicon-based devices are simultaneously required while emitting at a suitable emission wavelength to enable parallel optical interconnect modules with high bandwidth density, low cost per bandwidth and multiple terabit/s performance. The highest error-free bit rate of unpackaged VCSELs to date is 57 Gbit/s [1]. This result was achieved at room temperature with 850 nm oxide-confined VCSELs having a maximum −3 dB modulation bandwidth of ∼24 GHz [1]. By using similar 850 nm VCSELs with a smaller oxide-aperture diameter and a bandwidth of ∼26 GHz packaged in a module with an SiGe-based driver IC that incorporates feed forward equalisation and a custom-built highly sensitive and fast photo-receiver error-free operation at 64 Gbit/s was demonstrated [2]. Given the intrinsically higher temperature performance and higher potential differential gain of 980 nm VCSELs compared with 850 nm VCSELs we believe that VCSELs at longer wavelengths like 980 nm [3] are better suited as optical sources for VSR and on-chip optical interconnects. In this Letter, we present 980 nm VCSELs with −3 dB modulation bandwidths of 24.7 and 23 GHz at 25 and 85°C, respectively. Error-free operation is achieved at a record-high 46 Gbit/s at 85°C.

High-Speed VCSELs With Strong Confinement of Optical Fields and Carriers

“…where is the optical confinement factor, the active region volume, and the transport factor. Equation (6) clearly shows that the small VCSEL active region volume contributes to high resonance frequencies at low bias currents. It is also obvious from (6) that strong optical confinement from the short 2 ⁄cavity is advantageous.…”

“…46 Gbit/s at 85°C has been demonstrated using 980 nm VCSELs with 23 GHz bandwidth at high temperature [6]. Research exploring unconventional VCSEL structures, with coupled cavities for multiple resonance peaks, have demonstrated bandwidths up to 37 GHz [7,8].…”

“…In this paper we explore the limits of optical and electrical confinement by using the shortest possible cavity length and placing the current aperture as close as possible to the active region. High-speed data transmission using 980 nm VCSELs with similar confinement have previously been demonstrated [6,14]. We investigate the temperature dependent dynamic and static performance of our latest generation of high-speed oxideconfined 850-nm VCSELs with a focus on the impact of the short cavity and strong current confinement.…”

Высокоскоростные Полупроводниковые Вертикально-Излучающие Лазеры Для Оптических Систем Передачи Данных (Обзор)

“…Дальнейшее уменьшение размеров апертуры до 4.5−5 µm и уменьшение времени жизни фотонов в резонаторе путем увеличения толщины приповерхностного слоя РБО привело к увеличению частоты эффективной модуляции до 24.7 GHz и реализации безошибочной передачи данных на скорости 50 Gbit/s [102]. Следует отметить, что расположение оксидной токовой апертуры в микроре-зонаторе относительно активной области также оказывает влияние на быстродействие ВИЛ.…”

High Speed and High Temperature Operation of VCSELs

“…It is therefore not surprising that 980 nm is the wavelength where error-free unequalized data transmission (bit-error-rate (BER) < 10 -12 ) at the highest reported speed to date at 85 °C of 46 Gb/s was recently demonstrated [1]. Nevertheless, high speed MMF such as OM4 is optimized for 850 nm and this is therefore the wavelength of most importance for datacom applications.…”