A new technique of optical ranging by a frequency-shifted feedback laser

Chirped comb generation in frequency shifted feedback DFB lasers

“…The FSF laser consists of a chirp frequency comb with a chirp rate of the order of 10 16 Hz/s. Such FSF lasers can overcome conventional limits on operating range and has allowed distance measurements of 3.7 km with a resolution of 9.4 mm [6] and 18.5 km with an a resolution of 20mm [7]. Both [6] and [7] used a Nd:YVO 4 crystal as a gain medium pumped by a diode laser.…”

“…Such FSF lasers can overcome conventional limits on operating range and has allowed distance measurements of 3.7 km with a resolution of 9.4 mm [6] and 18.5 km with an a resolution of 20mm [7]. Both [6] and [7] used a Nd:YVO 4 crystal as a gain medium pumped by a diode laser. Recent work has focused on the use of doped fibre ring lasers that employ a ring laser operating through an acoustic-optical modulator (AOM) and a seed laser [10].…”

“…The output of FSF lasers can exhibit a chirped structure covering a large continuous range of frequencies. These features can be used in various applications such as optical pumping, high precision optical frequencies measurement and optical frequency domain ranging (OFDR) [6,7]. These properties can also be used in various applications such as optical pumping [8] and measuring the separation of optical frequencies with high precision [9].…”

Experimental demonstration of impact of amplified spontaneous emission on devices based on cross-gain modulation in semiconductor optical amplifiers

“…5 Another technique uses a self-mixing effect and measures the distance using number of mode hops. 6 Nakamura et al 7 have used a frequency shifted feedback laser to measure distances with high accuracy. These schemes require an interferometer for their operation, except Ref.…”

Design and performance of a frequency chirped external cavity diode laser

“…The second method used to produce a frequency chirp of a diode laser is to provide frequency-shifted feedback ͑FSF͒ to the laser diode using an intra-cavity acousto-optic modulator ͑AOM͒. [13][14][15][16][17] The output of a laser diode is collimated and sent through the AOM and the first order beam is retroreflected back through the AOM with the first order beam providing the FSF. The slope of the frequency chirp is ␥ϭ FS / RT where FS is the frequency shift per round trip imparted by the AOM and RT is the cavity round trip time while the duration of the frequency chirp is 1/ FS .…”