This paper presents the design and experimental study of a coupled-cavity laser based on the micromachining technology for wide tuning range and improved spectral purity. The core part of this design utilizes a deep-etched movable parabolic mirror to couple two identical Fabry-Pérot chips and thus allows the active adjustment of the cavity gap so as to optimize the mode selection and to increase the tuning range as well. In experiment, the laser achieves the single longitudinal mode output over 51.3 nm and an average side-mode-suppression ratio of 22 dB when the tuning current varies from 5.7-10.8 mA. The measured wavelength tuning speed is 1.2 micros and the single mode output is stable at any wavelength when the tuning current is varied within +/- 0.06 mA. Compared with the conventional fixed cavity gap coupled-cavity lasers, such design overcomes the phase mismatching and mode instability problems while maintaining the merit of high-speed wavelength tuning using electrical current.
This paper presents a micromachined tunable laser that utilizes a silicon optical tunneling structure to tune both the polarization state and the wavelength of the laser output. The device is fabricated on silicon-on-insulator wafer using deep reactive ion etching. In experiment, the wavelength and the polarization are tuned by heating up the silicon optical tunneling structure via the thermo-optic effect. A 900 change of polarization direction is obtained using a heating current of 61.2 mA, and a wavelength tuning of 2 nm is also demonstrated. The output spectrum shows a high suppress ratio above 30 dB. Compared with the previous MEMS tunable lasers that have a random or fixed polarization state, this device provides a special capability in tuning the polarization state in addition to the wavelength, and would find niche applications in biomedical research, interferometry, coherent communications, instrumentations and sensors.
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