Uncooled 100-GBaud Directly Modulated Membrane Lasers on SiC Substrate

Abstract

We investigate the temperature dependence of the dynamic characteristics of a 1.3-m InGaAlAs-based directly modulated membrane laser on a SiC substrate. The laser is fabricated by combining direct wafer bonding of SiC and InP substrates using a very thin (~10 nm) oxide layer and epitaxial regrowth of a membrane InP layer on the InP/SiC template. The membrane laser structure on SiC with a high thermal conductivity (490 Wm -1 K -1 ) and a moderate refractive index (~2.6) ensures both high thermal dissipation and a large optical confinement factor in the active region, which are ideal for increasing the relaxation oscillation frequency even at high operating temperatures. We further leverage the optical feedback effect from the output facet of a waveguide to enhance the bandwidth and enable signal modulation at 100 GBaud and beyond. Owing to the high relaxation oscillation frequency and the photon-photon resonance effect, it is possible to obtain a flat frequency response at temperatures ranging from 25 to 85°C. The fabricated membrane laser on SiC with an active-region length of 50 m exhibits 3dB bandwidths of >110, 97, and 74 GHz at 25, 55, and 85°C, respectively. We successfully demonstrate 2-km transmissions of 100-Gbit/s NRZ signals under uncooled conditions (25 to 85°C). Furthermore, the laser is capable of 112-Gbit/s NRZ modulation at 85°C.

16-Channel Directly Modulated Membrane III-V Laser Array on SiO2/Si Utilizing Photon-Photon Resonance

“…uncooled operation of DML even up to 85 o C, our focus remains on our PPR membrane DMLs on high-thermal-conductivity SiC substrates [15].…”

“…However, the intrinsic (i.e., carrier-photon) dynamics in DMLs impose limitations on the achievable bandwidth based on the relaxation oscillation frequency (𝑓 𝑅 ), which, in turn, is proportional to the square-root of the operating bias current (𝐼 𝑏 ) above threshold (𝐼 𝑡ℎ ) , 𝑓 𝑅 ∝ √𝐼 𝑏 − 𝐼 𝑡ℎ , leading to an intrinsic power consumption -bandwidth tradeoff [11,12]. To address this tradeoff, laser designs incorporating integrated optical feedback that take advantage of cavity and longitudinal modal effects [14][15][16][17][18][19][20][21][22][23], notably the photon-photon resonance (PPR) effect, can be used to boost DML bandwidths by over 2 times without the need to increase the bias current. Using such PPR-enabled designs, we have previously demonstrated a record 108 GHz DML bandwidth over a membrane laser fabricated on a highthermal-conductivity SiC substrate [14] and a ~60 GHz, S. Yamaoka was previously with NTT Device Technology Labs, Nippon Telegraph and Telephone Corporation, Atsugi, Kanagawa, 243-0198 Japan and now he is with NTT Access Network Service Systems Labs, Nippon Telegraph and Telephone Corporation, Yokosuka, Kanagawa, 239-0847 Japan (e-mail: suguru.yamaoka@ntt.com).…”

Efficient heat sink by ultrathin BCB bonding for InP membrane lasers

“…For wafer-scale integration, recently RT direct bonding on surface-activated SiO 2 helped to reduce the thermal impedance, 17) also on a 2 inch wafer scale with SiO 2 thickness of only 10 nm. 18) However, the process of direct surface-activated bonding on SiO 2 puts high requirements on surface cleanness, low roughness, and a high level of planarization; otherwise, defects are inevitable on a wafer scale. That is why direct bonding is mostly used for active devices with lateral current injection, such as in Ref.…”

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].…”