Simultaneous lasing at up to 24 wavelengths is demonstrated in an erbium-doped fiber-ring laser using a simple design. This result is achieved using a low-loss cavity, controlled polarization evolution and liquid nitrogen cooling to enhance spectral hole-burning, polarization hole-burning, and polarization selectivity. The design does not include any wavelength-selective components; instead, it utilizes wavelength selectivity provided by polarization evolution in the cavity. The amplitude variation between emission peaks is less than 3 dB over a 17-nm spectral range. A narrow linewidth of 0.15 nm, dense line spacing of 1.1 nm, and a good signal-to-noise ratio of more than 30 dB are achieved over most of the erbium bandwidth. The comb spectrum location and width are adjustable by changing and adjusting cavity components.

24-line multiwavelength operation of erbium-doped fiber-ring laser

We demonstrate a wide and fast wavelength-tunable modelocked fiber laser based on tuning the mode-locking frequency. The laser is in a sigma-laser configuration, and a wideband semiconductor optical amplifier (SOA) at 1.3 mum wavelength region is used as a gain medium. Mode locking is achieved by direct modulation of the injection current to the SOA, and a dispersion compensation fiber (DCF) is used to provide desired intracavity dispersion. By tuning the modulation frequency, a wide tuning range over 100 nm is achieved. Lasing wavelength is measured to be linearly in proportion to the RF frequency applied to the SOA. The sweep rate over the entire wavelength range (100 nm) can be raised to be as high as 200 kHz.

Wide and fast wavelength-tunable mode-locked fiber laser based on dispersion tuning.

A laser system capable of efficient production of high energy sub-nanosecond pulses in the 2-15 um spectral region is disclosed Diode pumped solid state lasers are used as pump sources The system design is simple, reliable and compact allowing for easy integration The laser system includes a combination of compact solid-state ~1 micron laser sources, producing high power picosecond pulses, with optical parametric amplification and a quasi-continuous wave laser for seeding the amplification process that enables the efficient conversion of the high power ~1 micron laser radiation to tuneable mid-infrared sub-ns pulses New parametric processes are presented for achieving high gains in bulk nonlinear crystals Furthermore, a method of exceeding the fundamental conversion efficiency limit of direct three wave mixing is presented The compact and robust nature of this novel laser system opens up the use of high power and high peak power mid-infrared laser pulses to a wide variety of important medical and dental applications

LASER SYSTEM FOR GENERATION OF HIGH-POWER SUB- NANOSECOND PULSES WITH CONTROLABLE WAVELENGTHS IN 2-15 µm REGION

Control of nonlinearity is a challenge in fiber amplifiers designed to generate pulses of a few picoseconds duration, and as a result, picosecond fiber amplifiers have failed to reach peak power of 1MW. Divided-pulse amplification, combined with the use of circular polarization, allows the generation of 2.2 ps pulses with energy as high as 2.5 μJ and peak power of 1 MW.

Generation of megawatt peak power picosecond pulses from a divided-pulse fiber amplifier

We report a tenfold stability improvement in the mean wavelength variations induced by polarization fluctuations in an Er-doped superfluorescent fiber source. This was accomplished by replacing the mirror in a double-pass source with a Faraday rotator mirror, thereby nearly eliminating polarization dependent gain. The resulting mean wavelength variations of less than 3.5 parts-per-million (limited by the detection noise floor), approach the requirement for inertial-grade fiber optic gyroscopes.

A polarization-stable Er-doped superfluorescent fiber source including a Faraday rotator mirror

We present a detailed study of the polarization properties of a reflective fiber amplifier composed of a circulator, a normal single-mode Er-doped fiber and a Faraday rotator mirror. The amplifier can preserve an arbitrary input state of polarization regardless of any external perturbations, and is completely free from polarization effects. The effect of imperfections of the Faraday rotator mirror is also discussed. Finally, we demonstrate experimentally the polarization-stability of the amplifier and its ability to compensate polarization mode dispersion both in the circulator and in the single-mode Er-doped fiber.

M. Ito

Papers

Polarization properties of a reflective fiber amplifier employing a circulator and a Faraday rotator mirror