C. Svelto

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.

WIDELY TUNABLE SINGLE-FREQUENCY ERBIUM-YTTERBIUM PHOSPHATE GLASS LASER

A tunable, single‐frequency, diode‐pumped miniature Er:Yb:glass laser of high power is described. The laser exhibits two intervals of continuous tuning, from 1549 to 1563 nm (Δλ=14 nm) and from 1531 to 1540 nm (Δλ=9 nm), respectively. For an input pump power of 140 mW, a single frequency output power of 20 mW at 1563 nm has been obtained. The tuning characteristics are found to be strictly related to the gain–loss balance of the laser cavity.

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.

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.

Three-Dimensional Reconstruction and Image Processing in Mandibular Distraction Planning

Mandible or facial bone reconstruction is a serious challenge in craniomaxillofacial surgery. Careful presurgical planning or availability of objective methods to evaluate the three-dimensional (3-D) shape of the patient mandible is necessary to achieve predictable outcomes. The aim of this paper is to apply 3-D techniques of volumetric reconstruction and image processing for planning distraction osteogenesis of the mandible, involving the use of 3-D modeling. To accomplish this task, suitable two-dimensional (2-D)-to-3-D image processing is used in order to obtain a 3-D model of the mandible from standard 2-D computed tomography images. The goal of this paper is to provide the surgeon with a 3-D model of the patient mandible, where it would be possible to find, in the presurgical phase, the exact point of implant with respect to the patients anatomy and to build a custom-made prosthesis that properly fits the bone surface of the patient for correct control of the vector during the progressive traction of the bone segments

High-Resolution Mode-Locked Laser Rangefinder With Harmonic Downconversion

The development of new pulsed optical sources with high pulse stability allows the improvement of common contactless measurement techniques. A new two-way optical rangefinder, employing a femtosecond laser, is presented here from design to implementation. The system is based on the evaluation of the phase delay of the returning optical pulse train with respect to the outgoing one. The main idea is to expand the time interval corresponding to the phase delay by harmonic heterodyne downconversion of a high harmonic of the pulse repetition rate (up to 10 GHz), which is applied symmetrically to the two channels. The system has shown 10 repeatability with a resolution that improves proportionally to the number of the employed harmonic.

Suppression of intensity noise in a diode-pumped Tm–Ho:YAG laser

We investigate the intensity noise induced by pump-power fluctuations in a diode-pumped single-frequency codoped Tm-Ho:YAG laser and we measure, in the frequency domain, the corresponding transfer function. Good agreement between the measured transfer functions and the theoretical prediction is found. A relative intensity-noise level of ~- 110 dB/Hz from ~1 kHz to the relaxation-oscillation frequency, with complete suppression of the relaxation-oscillation peak, is achieved by use of a suitable optoelectronic feedback circuit.

Time of flight telemeter with picosecond modelocked laser

In this work is presented the design and the preliminary promising experimental results obtained by our new two-way time-of-flight telemeter. The system is based on the evaluation of the phase delay of the returning optical pulses train with respect to the outgoing one, generated from a femtosecond laser. The main idea is to expand the phase difference time delay measured with the adoption of a heterodyne method, beating at high harmonic, till 10 GHz, applied symmetrically to the two channels. It is expected that micrometer absolute accuracies and better repeatability can be obtained in this way than in simple time of flight telemetry.

Three colors particle image velocimetry using flashed lamps as light source

In the last few years. Particle Image Velocimetry (PIV) has, become one of the most useful techniques for the study of flowfields. In 2D applications, it allows the simultaneous measurement of the velocity distribution on the whole acquisition area. Currently, the main limits to a further diffusion of this technique are economic and safety issues. Laser illumination, commonly used for PIV measurement systems, is expensive and the use of laser beams is limited by some problems, primarily safety. Other typical aspects of PIV techniques are the limits on the velocity range that can be measured simultaneously with adequate accuracy and the difficulty in using relatively thick light sheets. Upon considering the above problems and our previous experience in PIV with flashed lamps as light source, with the related problems of highly noisy images, we designed and built a new PIV. acquisition system which uses three colored lamp flashes as a light source. This solution can give some significant advantage in several aerodynamic and hydrodynamic situations. This recently developed PIV acquisition system is fully transportable, eyesafe, practical, and economic (2500 USD). Moreover it allows high flexibility for velocity measurements and independent setting of.. different, acquisition parameters.