# 47.5 GHz Membrane-III-V-on-Si Directly Modulated Laser for Sub-pJ/bit 100-Gbps Transmission  
[PERSON] 1,*  
1 NTT Device Technology Labs, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198, Japan; [EMAIL_ADDRESS] (S.Y. ); [EMAIL_ADDRESS] (T.F. ); [EMAIL_ADDRESS] (H.N. ); [EMAIL_ADDRESS] (K.T. ); [EMAIL_ADDRESS] (T.T. ); [EMAIL_ADDRESS] (T.K. ); [EMAIL_ADDRESS] (S.M.) 2 Graduate School of Information, Production and Systems, Waseda University, Kitakyushu-shi, Fukuoka 808-0135, Japan
* Correspondence: [EMAIL_ADDRESS]  
[PERSON] 1, [PERSON] 1, [PERSON] 1, [PERSON] 1, [PERSON] 1, [PERSON] 1,2 and [PERSON] 1  
1 NTT Device Technology Labs, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198, Japan; [EMAIL_ADDRESS] (S.Y. ); [EMAIL_ADDRESS] (T.F. ); [EMAIL_ADDRESS] (H.N. ); [EMAIL_ADDRESS] (K.T. ); [EMAIL_ADDRESS] (T.T. ); [EMAIL_ADDRESS] (T.K. ); [EMAIL_ADDRESS] (S.M.) 2 Graduate School of Information, Production and Systems, Waseda University, Kitakyushu-shi, Fukuoka 808-0135, Japan
* Correspondence: [EMAIL_ADDRESS]  
M. K.  
low-power DMLs based on our novel membrane-III-V-on-Si technology [5; 6; 7; 8]. Owing to such a thin-film (<350 nm thick) InP-based layer buried on SiO\({}_{2}\), we can achieve high optical and carrier confinements, which is beneficial both for reducing the power consumption and increasing the modulation speed. Meanwhile, the \"on-Si\" fabrication allows us to potentially use large Si wafers and existing CMOS processes for further cost reduction, while we have also demonstrated the co-integration of SiO\({}_{\text{x}}\)-based spot-size converters [6] and SiN-based arrayed waveguide grating (AWG) for space- and wavelength-division multiplexing (SDM/WDM) systems [7; 8]. The aforementioned membrane DMLs on Si had previously achieved 3-dB bandwidths of around 20 GHz, which enabled us to use them for demonstrating 28 GBaud PAM-4 (56 Gbps) signals with sub-pJ/bit efficiencies [5]. However, due to the intrinsic characteristics of the carrier-photon resonances (CPR) in DMLs, further increases in the modulation speed would require an increase of the bias current of these devices. This effectively translates to an increase of the transmitter's power consumption, which hinders DMLs' energy-efficiency capabilities. Recently, a solution has emerged that effectively alleviates this power-bandwidth tradeoff by introducing detuned-loading (DL) and photon-photon resonance (PPR) effects via specialized longitudinal laser designs [9; 10; 11; 12; 13; 14; 15; 16; 17]. The DL and PPR effects can be used to effectively boost the high-frequency components of the modulated signal and effectively extend the 3-dB bandwidth of the DML beyond the levels allowed by the intrinsic CPR effect. In particular, in the recent years, two methods have attracted attention to generate these effects: (a) a method based on including a passive feedback waveguide [12; 13; 14; 15; 16; 17] and (b) a method based on including a distributed Bragg reflector (DBR) [9; 10; 11; 12]. Based on the first method (i.e., passive feedback), we have recently demonstrated DMLs with record-high bandwidths in excess of 100 GHz [17], capable of accommodating net data rates up to 325 Gbps (gross rates > 400 Gbps) [18]. These DMLs were based on our novel membrane-III-V-on-SiC technology, which enabled record-high intrinsic CPR-based 3-dB bandwidths of around 60 GHz, due to the high-thermal conductivity properties of the SiC substrate [17]. Therefore, the bandwidth enhancement due to the DL and PPR effects on such \"on-SiC\" DMLs was around 1.8x times. In this paper, we expand on our recently published work [12], in which we demonstrated a bandwidth extension for our membrane DMLs on Si by introducing a DL and PPR-generating longitudinal design based on the DBR method. In particular, a single-mode membrane DML on Si with a maximum 3-dB bandwidth of 47.5 GHz in the O-band was demonstrated, which equals to a bandwidth enhancement of around 2.4x times compared to our previous CPR-based designs [5; 6; 7].