Extremely energy-efficient oxide-confined high-speed 850 nm vertical-cavity surface-emitting lasers for optical interconnects are presented. Error-free performance at 17 and 25 Gb/s via a 100 m multimode fiber link is demonstrated at record high dissipation-power-efficiencies of up to 69 fJ/bit ͑Ͻ0.1 mW/ Gbps͒ and 99 fJ/bit, respectively. These are the most power efficient high-speed directly modulated light sources reported to date. The total energy-to-data ratio is 83 fJ/bit at 25 °C and reduces to 81 fJ/bit at 55 °C. These results were obtained without adjustment of driving conditions. A high D-factor of 12.0 GHz/ ͑mA͒ 0.5 and a K-factor of 0.41 ns are measured.
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.
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