Young Tak Han

A 10 × 10 Gb/s DFB laser diode array fabricated using a SAG technique

We present a ten-channel distributed feedback laser diode array (DFB-LDA) developed for the transmission of 100-Gb/s (10 × 10 Gb/s) signals separated by an 8 nm wavelength grid at a center wavelength of 1.55 μm. For the fabrication of this type of laser array, a selective area growth (SAG) technique, electron-beam lithography, and a reverse-mesa ridge waveguide LD processing technique were adopted to offer a tailored gain spectrum to each channel, providing both accurate lasing-wavelength control and excellent single-mode yield over all channels, and reducing the fabrication cost and electrical and thermal resistances. To evaluate the operational performance of the fabricated chip systematically, we also developed a sub-assembly module containing a ten-channel λ/4-shifted DFB-LDA, ten matching resistors, flexible printed circuit board (FPCB) wiring, and a thermistor on a metal optical bench. The static and dynamic properties of all channels of the fabricated array are examined in this paper. The developed sub-assembly module shows a side-mode suppression ratio (SMSR) of > 50 dB, a modulation bandwidth of > 10 GHz, and a clear eye-opening before and after a 2-km transmission with dynamic extinction ratio of > 5 dB.

Improvement of modulation bandwidth in electroabsorption-modulated laser by utilizing the resonance property in bonding wire

We present and demonstrate a simple and cost-effective technique for improving the modulation bandwidth of electroabsorption-modulated laser (EML). This technique utilizes the RF resonance caused by the EML chip (i.e., junction capacitance) and bonding wire (i.e, wire inductance). We analyze the effects of the lengths of the bonding wires on the frequency responses of EML by using an equivalent circuit model. To verify this analysis, we package a lumped EML chip on the sub-mount and measure its frequency responses. The results show that, by using the proposed technique, we can increase the modulation bandwidth of EML from ~16 GHz to ~28 GHz.

A Multi-Channel Etched-Mesa PBH DFB Laser Array Using an SAG Technique

We present a multi-channel λ/4-shifted distributed feedback laser diode array (DFB-LDA) for the low-cost application of wavelength division multiplexing-based datacenter networks. The gain spectrum and lasing wavelength of each channel are controlled by utilizing selective area growth and E-beam lithography techniques, respectively. To reduce the power consumption and improve the channel uniformity of the proposed array, a planar-buried hetero-structure (PBH) is introduced and the region containing the active region and the current blocking structures are etched in a mesa form (i.e., an etched mesa PBH). From this study, it was found that an 8-channel 300-μm -long anti-reflection (AR) λ/4-shifted DFB-LDA has a threshold current of 10 mA, ±1.5 mA, and a side mode suppression ratio of over 50 dB for all channels. A transmission test for this LDA showed a clear eye opening with a dynamic ratio of over 4.5 dB at 10 Gb/s, and a power penalty of less than 2 dB after a 2-km transmission.