TUNABLE LASERS
Simple and tunable
Opt. Express 18,8392?8399 (2010)

  Tunable lasers are important for many applications in photonics, particularly for optical sensing, optical coherence tomography, and optical communications based on wavelength-division multiplexing. However, most tunable lasers only achieve wide tunability at the expense of cost or complexity. Kyung-Jo Kim and co-workers from Korea have now developed a compact and simple tunable laser that can be modulated simply through the mechanical bending of the device. Their scheme involves a highly elastic polymeric Bragg reflector coupled to a superluminescent laser diode to form an external feedback laser. When tensile strain is applied to the reflector, the grating period changes and so the reflection wavelength is shifted to shorter or longer wavelengths. By applying strains from ?36,000 με to 35,000 με, a continuous tuning range of 100 nm was achieved. However, to ensure reproducible operation, a smaller strain range of 57,000 με was also tested, producing a wavelength tuning range of 80 nm, between 1,495 nm and 1,575 nm. The laser demonstrates a much wider tuning range than silica fibre Bragg gratings or thermo-optic-tuned polymer devices, and may have commercial applications in piezoelectric motors.