60 GHz Bandwidth Directly Modulated Membrane III-V Lasers on SiO₂/Si

Abstract

Increasing demand for higher data rates in data centers and high-performance computing systems require optical interconnects that support more than 100 Gbps-per-lane. Meanwhile, as optics are packed ever closer to Ethernet switches and electronic processors, both operating temperatures and power consumptions increase, resulting in increasing operational and environmental costs. In this work we present our recent results on a two-channel energy-efficient directly-modulated membrane laser array on SiO2/Si with ~60-GHz 3-dB bandwidth, that can support both 100 Gbps-per-lane modulations as well as very small form-factors and power consumptions. The extension to 60 GHz bandwidths denotes a ~26.3 % increase compared to previous works, and it was achieved based on an optimized distributedreflector laser design for maximizing the photon-photon resonance effect. Based on the fabricated two-channel DML array, 200 Gbps (2×112-Gbps NRZ) with laser operating energy-per-bit cost of less than 0.3 pJ/bit over 2-km transmissions, and the feasibility of 400 Gbps (2×200-Gbps PAM-4) transmissions are demonstrated. Finally, the temperature dependence of the PPR effect and its impact on the E-O response have been studied both experimentally and with numerical simulations for temperatures up to 75 o C for the first time.

Uncooled 100-GBaud Directly Modulated Membrane Lasers on SiC Substrate

“…To the best of our knowledge, these f 3dB values are all records for DMLs. Note that membrane lasers on SiO 2 /Si using the PPR effect exhibited f 3dB values of 60, 54, and 46 GHz at 25, 50, and 70°C respectively [17]. In comparison, this membrane laser on SiC with an f r peak of around 30 GHz and f 3dB of 74 GHz at 85°C demonstrates that the high thermal conductivity of SiC helped suppress degradation of the differential gain with increasing bias current.…”

“…Although this approach succeeded in improving the f r , its value remained at around 20 GHz. The second approach is to use optical feedback techniques, including the detuned-loading and photon-photon resonance (PPR) effects, to generate optical filters and extra modes besides the lasing mode, which enhances the f r itself and adds an extra peak in the frequency response [7]- [17]. By applying these effects, a 55-GHz bandwidth was achieved with distributed reflector (DR) lasers, whose intrinsic bandwidth was ~30 GHz, on an InP-based platform [13].…”

“…However, these results were obtained at 25°C, and there has been no demonstration of 100-GBaud modulations of any DML at a temperature higher than 25°C. The next challenge is thus to achieve high-temperature 100-GBaud operation; however, it is challenging to achieve a flat small-signal response with the PPR effect because the f r decreases at high temperatures [16], [17], mainly because of degradation of the differential gain. There is also an issue of how the PPR frequency changes with temperature [17].…”

“…The next challenge is thus to achieve high-temperature 100-GBaud operation; however, it is challenging to achieve a flat small-signal response with the PPR effect because the f r decreases at high temperatures [16], [17], mainly because of degradation of the differential gain. There is also an issue of how the PPR frequency changes with temperature [17]. In principle, membrane lasers on high-thermal-conductivity SiC are ideal for achieving a high f r and f 3dB even at high temperatures because of the small self-heating effect, which reduces the degradation of the differential gain.…”

200 Gb/s Optical-Amplifier-Free IM/DD Transmissions using a Directly Modulated O-band DFB+R Laser targeting LR Applications

“…On the one hand, external modulator-based transmitters such as silicon-photonic [5,6], plasmonic [7][8][9], and thin-film Lithium Niobate-(TFLN) [10][11][12][13] Mach-Zehnder modulators (MZM) or micro-ring modulators (MRM) [14][15][16] have shown excellent performance in terms of bandwidth and modulation linearity for high baud rate operation, however, requiring high-power external light sources to operate. On the other hand, monolithically integrated transmitters such as electro-absorption modulated lasers (EML) [17][18][19][20][21][22][23][24][25] and directly modulated lasers (DML) [26][27][28][29][30][31] with a potentially smaller footprint and lower power consumption, also show promising characteristics in supporting over 200 Gb/s/lane transmissions. Moreover, recent efforts in monolithically integrating laser sources with TFLN modulators have been reported [32].…”