S. Taccheo

Femtosecond writing of active optical waveguides with astigmatically shaped beams

We describe a novel approach for the fabrication of optical waveguides by focused low-repetition-rate femtosecond laser pulses. This approach overcomes the main limitation of the technique, i.e., the strong asymmetry of the waveguide profile. By use of an astigmatic beam and suitably controlling both beam waist and focal position in tangential and sagittal planes, it is possible to shape the focal volume in such a way as to obtain waveguides with a circular transverse profile and of the desired size. This technique is applied to the fabrication of active waveguides in Er:Yb-doped glass substrates. The waveguides are single mode at 1.5 μm and exhibit propagation losses of ∼0.25 dB/cm and an internal gain of 1.4 dB at 1534 nm.

Erbium–ytterbium microlasers: optical properties and lasing characteristics

Abstract In this paper we present a comprehensive review of the work done by our group on diode-pumped bulk erbium–ytterbium microlasers. Starting from an analysis of the optical properties of Er–Yb doped phosphate glasses, addressed to the modeling of the active material and to the design and optimization of laser cavities, different operating regimes and peculiar properties of these novel laser devices are described and discussed, including multi-longitudinal mode and single-frequency operation, frequency tuning and stabilization, intensity stabilization, Q-switching, mode-locking and frequency-modulation operation. Due to the high performance in terms of emission characteristics and potential low cost, these microlasers are attractive for a large number of applications and, in particular, for optical communications at 1530–1560 nm wavelengths, metrology, and telemetry at an eye-safe wavelength.

Diode-pumped bulk erbium-ytterbium lasers

A comprehensive review of the work done by our group, during the last few years, on diode-pumped cw operating bulk Er : Yb phosphate glass is presented. The high performance of this laser in terms of output power, laser slope efficiency, single longitudinal and transverse mode operation, laser tunability and frequency stability, amplitude noise, and active mode-locking operation, are considered. The combination of this high performance and potential low cost makes these laser devices attractive for a variety of applications including spectroscopy, metrology, optical radars, optical communications, and all optical switching.

Diode-pumped microchip Er-Yb:glass laser.

A single-frequency, diode-pumped, Er-Yb:glass microchip laser at a 1530-nm wavelength has been designed and operated. An output power of greater than 25 mW, a linewidth narrower than 1 kHz, and a slope efficiency of 22% have been obtained.

EXPERIMENTAL ANALYSIS AND THEORETICAL MODELING OF A DIODE-PUMPED ER:YB:GLASS MICROCHIP LASER

A comprehensive study of a diode-pumped Er:Yb:glass microchip laser, operating at 1530-nm wavelength, is presented. The operating conditions wherein a linearly polarized, single longitudinal and transverse mode operation is achieved are indicated. An optimum pump spot size that minimizes the threshold pump power and maximizes the slope efficiency is experimentally found and theoretically justified by a space-dependent rate-equation model.

Single-mode cw erbium–ytterbium glass laser at 1.5 μm

Single-mode operation of a continuous-wave Er:Yb:phosphate glass laser pumped at 980 nm by a InGaAs index-guided diode laser has been achieved for what is to our knowledge the first time. The maximum output power obtained at 1540 nm is 10 mW, and the width of the spectral line is less than 15 kHz.

A diode‐pumped nonlinear mirror mode‐locked Nd:YAG laser

We report on passive mode‐locking of a cw diode‐pumped Nd:YAG laser using the nonlinear mirror technique. The nonlinear mirror is made by a lithium triborate frequency doubling crystal and a dichroic mirror that partially transmits the fundamental frequency and totally reflects the second harmonic. The laser produces nearly transform‐limited pulses of 10 ps duration and 700 mW average power, with a slope efficiency of 28%. The mode‐locking is self‐starting under optimized conditions. Long term stability requires accurate control of the crystal temperature.

Analysis of amplified spontaneous emission: some corrections to the Linford formula

The behaviour of amplified spontaneous emission (ASE) in the low and high gain saturation regimes and for both a Lorentzian and Gaussian line is critically reconsidered. Quite consistent corrections to a well known and widely adopted formula have been found for the ASE intensity in the low saturation regime. Computer calculations validate these corrections and indicate the degree of approximation involved.

2.5 GHz and 5 GHz harmonic mode-locking of a diode-pumped bulk erbium-ytterbium glass laser at 1.5 microns

Third-order harmonic mode locking of a diode-laser pumped bulk Er:Yb:glass laser by frequency modulation with a lithium niobate modulator is reported. Stable pulses at a repetition rate of 2.5 and 5 GHz with a pulse duration down to 9.6 ps are obtained. The average output power is 3 mW, the pulse peak power is 120 mW at 2.5 GHz repetition rate, and the pulses are approximately 1.4 times transform limited. The pulse duration can be increased up to 30 ps by decreasing the mode-locker drive power.<<ETX>>

Dynamic behavior of gain-clamped Er:Yb and high concentration Er-doped amplifier

All-optical gain-clamped erbium-ytterbium (Er : Yb)-doped amplifier dynamic response is modeled and investigated. The complex Er:Yb rate equation system is reduced to a single equation. This simplification gives a more intuitive understanding of relevant physical mechanisms of Er:Yb doping. Experiments confirm theoretical assumptions. Results also allow us to describe dynamics in highly doped Er devices such as waveguide amplifiers.