Tunable, single frequency erbium fiber laser using an overlay bandpass filter

Abstract

We describe a single frequency, unidirectional erbium fiber ring laser. Wavelength selection is performed by a ‘‘continuous fiber’’ filter of the fiber to planar waveguide coupler type. Varying the refractive index experienced by the exposed surface of the filter allowed the single longitudinal mode output from the laser to be tuned, discretely, from 1556–1561 nm with a resolution limited linewidth of 52 kHz.

An efficient local fundamental-mode cutoff for thermo-optic tunable Er3+-doped fiber ring laser

“…At 39.6°C, the inset plot in Fig. 4 shows the laser spectrum near the edge of the gain bandwidth and where the comb-like filtering phenomenon reflects the resonant coupling between the SPF and the top surface of the optical polymer, which occurs only when n o is substantially higher than the n eff [7]. The resonance spacing is around 0.79 nm and the resonant coupling can be eliminated by inducing roughness on top surface of the polymer or enhanced by improving the finesse to serve as a DWDM filter based on our SPFs with very long L eff .…”

“…Both of the Raman and Er 3+ -doped fiber amplifiers (EDFAs) can provide a very wide gain bandwidth of up to 100 nm and, for EDFAs, the laser amplification can occur at S-(1480 ~ 1520 nm) or C-(1530 ~ 1565 nm) or L-(1570 ~ 1610 nm) bands contingent upon the erbium ion concentration, length of the erbium-doped fiber (EDF) and/or amplified spontaneous emission (ASE) suppressing filter. Tunable Er 3+ -doped fiber lasers had been demonstrated using variant kinds of tunable filters [1][2][3][4][5][6][7][8][9]. Among them, the fundamentalmode cutoff wavelength (LP 01 -λ c ) induced from a depressed inner cladding is distinguished for wideband distributed ASE suppression and was employed to achieve tunable S-band EDFAs and fiber lasers [9,10].…”

“…The cross angle between the n(λ) curves is crucial to the sharpness of the cutoff, which is related to the linewidth of the fiber laser, and the thermo-optic coefficient dn D /dT is decisive to the temperature tuning ramp. Although SPFs had been used as filters in EDFRL [5][6][7][8], this is the first time that a side-polished shortpass filter, which provides a wideband tunable (> 400 nm) loss window with high rejection efficiency (> 45 dB/cm) for wavelengths longer than the cutoff and high tuning efficiency (26.7 nm/°C), is used to investigate the EDFRL with lasing wavelength tuning toward the shorter wavelengths through an efficient local ASE suppression in the resonator. It reflects that, based on such material dispersion discrepancy, tunable fiber short/long-pass or bandrejection filters could be employed to achieve tunable EDFAs and lasers covering S-, C-, and/or L-bands using variant optical polymers in the future.…”

70-nm tunable single-longitudinal mode erbium-doped fiber laser

“…There are other methods to generate an L-band single-mode laser (or any fiber single-mode laser), one of which is to use subcavities, as has been widely studied previously 9,11 . In our experiments, we tried two subcavities to produce a single-mode laser up to 1610 nm, but there was a lot of laser mode-hops in ordinary lab conditions.…”

“…Erbium-doped fiber lasers (EDFL) are interesting because of high output power, narrow line-width, low intensity noise and potentially all-fiber construction [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] . In the last decade, several single-mode erbium doped fiber lasers have been demonstrated by either using an un-pumped EDF as a narrow-bandwidth auto-tracking filter [2][3][4] , or by using a coupled fiber-ring-cavity-filter [8][9][10][11] . However, the tunable range was limited to less than about 40 nm 3 and, also, the laser was not continuously tunable-it had a tuning step of about 100 pm 4 .…”