Distributed Feedback Laser Diode Array Research Articles

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

We present a multi-channel $\lambda $ /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- $\mu \text{m}$ -long anti-reflection (AR) $\lambda $ /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.

Multi‐wavelength channel 1.5 μm and 10 Gb/s EMBH DFB‐LD array module using SAG technology

A multi-wavelength channel distributed feedback laser diode array (DFB-LDA) for the low-cost and low-power consumption applications of WDM-based datacentre networks is reported. The gain spectrum and lasing wavelength of each channel are controlled by using selective area growth and E-beam lithography techniques, respectively. To reduce the operation current and parasitic capacitance of the proposed array, an etched mesa buried hetero-structure (EMBH) is introduced. From this study, it was found that an eight-channel 300 μm long λ/4-shifted DFB-LDA has a threshold current of 10 ± 1.5 mA and a side mode suppression ratio of over 50 dB at a current of 50 mA for all channels. A transmission test for this LDA showed a clear eye opening with a dynamic extinction ratio of over 4.5 dB at 10 Gb/s after a 2 km transmission.

Transmitter Optical Subassembly Using a Polarization Beam Combiner for 100 Gbit/s Ethernet over 40-km Transmission

A transmitter optical subassembly (TOSA) has been developed for a 100-Gbit/s Ethernet system for a long optical transmission distance over a 40-km single-mode fiber (SMF). To obtain a high optical output power and a high dynamic extinction ratio, the TOSA consists of two two-channel distributed feedback laser diode array chips integrated with electro-absorption modulators (EADFB laser array chips) with a 2 × 1 multimode interference (MMI) optical coupler and a polarization beam combiner for wavelength multiplexing. The TOSA is 8.7 mm × 28.7 mm × 6.5 mm including an LC-type receptacle. The TOSA has a twin collimator path for two EADFB laser array chips. The wavelength multiplexer consists of a mirror, a half-wavelength plate, and a polarization beam combiner. The TOSA could improve the optical output power by around 2 dB compared with a TOSA with a four-channel EADFB laser array chip and a 4 × 1 MMI optical coupler. An optical modulation amplitude of over 0.5 dBm and a mask margin exceeding 21% were obtained for each lane when all lanes were operated simultaneously with an EA modulator driving voltage of 1.5 V at a bit rate of 25.78125 Gbit/s, which fully satisfies the 100GBASE-ER4 specifications. We demonstrated error-free operation for an SMF transmission of over 40 km. Moreover, we confirmed that the TOSA was capable of error-free SMF transmission over 60 km with a power penalty of less than 1.4 dB.

A <inline-formula> <tex-math notation="TeX">\(10 \times 10\) </tex-math></inline-formula>-Gb/s DFB-LD Array Integrated With PLC-Based AWG for 100-Gb/s Transmission

We describe a hybrid integration module of a 10 × 10-Gb/s distributed feedback laser diode array (DFB-LDA) and a planar light-wave circuit-based arrayed waveguide grating (AWG). For fabrication of the DFB-LDA, we adopted a selective area growth technique to tailor the channel gain properly, and E-beam lithography to accurately control the channel lasing wavelength and grating phase. For implementation of the AWG, we introduced a 2%-Δ structure to reduce the coupling loss between the AWG and DFB-LDA, and designed the tapered and parabolic waveguides at the junctions of the free propagation regions to widen the spectral passband width (i.e., a -1-dB spectral width of 3 nm). The developed module shows a side-mode suppression ratio of >45 dB, a clear eye opening with a dynamic extinction ratio of >4.4 dB at 10 Gb/s, and a power penalty of <;1.5 dB after a 2-km transmission for all channels.

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.

Reducing electrical crosstalk in laser-diode array modules by using a film-carrier interconnection

Interconnecting the laser-diode (LD) arrays in a LD array module with a film-carrier reduces electrical crosstalk by about 8 dB. This value agrees well with the analytical value of 10 dB obtained by SPICE simulation. Application of this new technique to a prototype four-channel dual-electrode distributed-feedback LD array module for optical frequency-division-multiplexing achieved a flat response up to 2.3 GHz and a crosstalk of less than 30 dB for frequencies below 1 GHz. >