M P Kalita

Bismuth doped fiber laser and study of unsaturable loss and pump induced absorption in laser performance

A short Bi doped fiber laser operating in the wavelength region of 1160-1179 nm has been demonstrated. The influence of unsaturable loss on laser performance is investigated. Excited state absorption in Bi doped germano-alumino silicate fiber is reported in the 900-1300 nm wavelength range under 800 and 1047 nm pumping. Bi luminescence and fluorescence decay properties under different pumping wavelengths are also investigated.

Multi-watts narrow-linewidth all fiber Yb-doped laser operating at 1179 nm.

An all-fiber, narrow-linewidth, high power Yb-doped silica fiber laser at 1179 nm has been demonstrated. More than 12 W output power has been obtained, corresponding to a slope efficiency of 43% with respect to launched pump power, by core-pumping at 1090 nm. In order to increase the pump absorption, the Yb-doped fiber was heated up to 125 degrees C. At the maximum output power, the suppression of amplified spontaneous emission was more than 50 dB. Furthermore, theoretical work confirms that the proposed laser architecture can be easily scaled to higher power.

Wideband EDFA Based on Erbium Doped Crystalline Zirconia Yttria Alumino Silicate Fiber

A wideband erbium-doped fiber amplifier (EDFA) is demonstrated using an Erbium-doped zirconia fiber as the gain medium. With a combination of both Zr and Al, we could achieve a high erbium doping concentration of 4320 ppm in the glass host without any phase separations of rare-earths. The Erbium doped fiber (EDF) is obtained from a fiber preform, which is fabricated in a ternary glass host, zirconia-yttria-aluminum codoped silica fiber using a MCVD process. Doping of Er2O3 into Zirconia yttria-aluminosilicate based glass is done through solution doping process. The maximum gain of 21.8 dB is obtained at 1560 nm with 2 m long of EDF and co-pumped with 1480 nm laser diode. At high input signal of -4 dBm, a flat-gain at average value of 8.6 dB is obtained with a gain variation of less than 4.4 dB within the wavelength region of 1535-1605 nm and using 3 m of EDF and 100 mW pump power. The corresponding noise figure is maintained below 9.6 dB at this wavelength region.

Excited state absorption measurement in the 900-1250 nm wavelength range for bismuth-doped silicate fibers

The feasibility of direct laser diode pumping of Bi-doped fiber lasers at the wavelengths of 915 and 975 nm was examined by measuring excited state absorption in Bi-doped silicate fibers for the wavelength range of 900-1250 nm. When the Bi-doped fibers were pumped at 1047 nm a strong excited state absorption was found at 915 and 975 nm, whereas no significant excited state absorption was observed in the 1080 nm pumping band nor in the emission band, approximately 1160 nm, of Bi-doped fiber lasers.

Performance comparison of Zr-based and Bi-based erbium-doped fiber amplifiers.

In this Letter, we present a comprehensive comparison of the performance of a zirconia-based erbium-doped fiber amplifier (Zr-EDFA) and a bismuth-based erbium-doped fiber amplifier (Bi-EDFA). The experimental results reveal that a Zr-EDFA can achieve comparable performance to the conventional Bi-EDFA for C-band and L-band operations. With a combination of both Zr and Al, we could achieve a high erbium-doping concentration of about 2800 ppm (parts per million) in the glass host without any phase separations of rare earths. The Zr-based erbium-doped fiber (Zr-EDF) was fabricated using in a ternary glass host, zirconia-yttria-aluminum codoped silica fiber through a solution-doping technique along with modified chemical vapor deposition. At a high input signal of 0 dBm, a flat gain at average value of 13 dB is obtained with a gain variation of less than 2 dB within the wavelength region of 1530-1575 nm and using 2 m of Zr-EDF and 120 mW pump power. The noise figures are less than 9.2 at this wavelength region. It was found that a Zr-EDFA can achieve even better flat-gain value and bandwidth as well as lower noise figure than the conventional Bi-EDFA.

Fiber design for high-power fiber lasers

This paper reviews the progress in active fibers suitable for power scaling, highlighting the advances in fiber design that will enable the control of nonlinearities such as SRS and SBS in high power fiber lasers, as well as making feasible a practical high power three-level system.

488 nm irradiation induced photodarkening study of Yb-doped aluminosilicate and phosphosilicate fibers

Photodarkening in highly Yb-doped aluminosilicate and phosphosilicate fibers, under 488 nm irradiation, is presented. Both irradiation-induced excess loss and post-irradiation temporal loss evaluations reveal that Yb-doped phosphosilicate fiber is highly resistant to photodarkening.

Influence of cooling on a bismuth-doped fiber laser and amplifier performance

We characterize bismuth-doped fibers under different excitation wavelengths. The fiber laser performance at 1179 nm was investigated, incorporating different cooling arrangements. Effective heat extraction can reduce the temperature-dependent unsaturable loss in fiber, resulting in increased laser performance. The operation of a bismuth-doped fiber amplifier at 1179 nm, at both low and high input signals, is also examined. The amplifier efficiency and the saturation power both depend on effective fiber cooling.

Study of Multichannel Amplification in Erbium-Doped Zirconia-Yttria- Alumino-Silicate Fiber

We report signal amplification and output signal-to-noise ratio (SNR) for simultaneous four-channel amplification at C-band in the new type of erbium-doped fiber (EDF) having core glass compositions of zirconia-yttria-alumino-phospho-silicate (EDF-I). Performance of EDF-I is compared with two mostly used EDFs having core glass compositions of alumino-silicate (EDF-II) and germino-alumino-silicate (EDF-III). EDF-I produces the best result of maximum gain difference <; 2 dB with output SNR of >; 22 dB at input signal level of -30 dB·m/channel amplification.

Bismuth-doped fiber laser at 1.16 mm

We used a bismuth-doped fiber with high pump absorption, 1.2 dB/m, to make a short (25 m) Bi-fiber laser at 1.16 mum with 10% efficiency. We discuss the influence of host glass and unsaturable absorption.