We report a monolithic integrated dual-wavelength laser diode based on a distributed Bragg reflector （DBR） composite resonant cavity. The device consists of three sections, a DBR grating section, a passive phase section, and an active gain section. The gain section facet is cleaved to work as a laser cavity mirror. The other laser mirror is the DBR grating, which also functions as a wavelength filter and can control the number of wavelengths involved in the laser action. The reflection bandwidth of the DBR grating is fabricated to have an appropriate value to make the device work at the dual-wavelength lasing state. We adopt the quantum well intermixing （QWI） technique to provide low-absorption loss grating and passive phase section in the fabrication process. By tuning the injection currents on the DBR and the gain sections, the device can generate 0.596 nm-spaced dual-wavelength lasing at room temperature.
A tunable two-section amplified feedback laser, which employs an amplifier section as the integrated feedback cavity, is designed and fabricated for dual-mode operation with mode separation of 100 GHz. Detailed simulations and experimental characterizations on the performance of the laser are presented. Promising dual-mode emission with continuous tuning range over 16 GHz（87.41–103.64 GHz） is experimentally demonstrated.
Monolithic integration of four 1.55-μm-range InGaAsP/InP distributed feedback （DFB） lasers using varied ridge width with a 4 x 1-multimode-interference （MMI） optical combiner and a semiconductor optical amplifier （SOA） is demon- strated. The average output power and the threshold current are 1.8 mW and 35 mA, respectively, when the injection current of the SOA is 100 mA, with a side mode suppression ratio （SMSR） exceeding 40 dB. The four channels have a 1-nm average channel spacing and can operate separately or simultaneously.
A terahertz excitation source based on a dual-lateral-mode distributed Bragg reflector （DBR） laser working in the 1.5 μm range is experimentally demonstrated. By optimizing the width of the ridge waveguide, the fundamental and the first-order lateral modes are obtained from the laser. The mode spacing between the two modes is 9.68 nm, corresponding to a beat signal of 1.21 THz. By tuning the bias currents of the phase and DBR sections, the wavelengths of the two modes can be tuned by 2 nm, with a small strength difference （〈5 dB） and a large side-mode suppression ratio （SMSR 〉 45 dB）.
We report a direct, modulated bandwidth enhancement in a amplified feedback laser （AFL）, both experimen- tally and numerically. By means of fabricated devices, an enhanced -3 dB bandwidth of 27 GHz with an in-band flatness of ±3 dB is experimentally confirmed at 13℃. It is numerically confirmed that the modulated bandwidth of the AFL can be enhanced to two times its original bandwidth, with more controlled flexibility to realize a flat, small-signal response.
