Stefano Taccheo

Er:Yb-doped waveguide laser fabricated by femtosecond laser pulses

Laser action is demonstrated in a 20-mm-long waveguide fabricated on an Er:Yb-doped phosphate glass by femtosecond laser pulses. An output power of 1.7 mW with approximately 300 mW of pump power coupled into the waveguide is obtained at 1533.5 nm. Waveguides are manufactured with the 520-nm radiation from a frequency-doubled, diode-pumped, cavity-dumped Yb:glass laser operating at a 166-KHz repetition rate, with a 300-fs pulse duration.

Femtosecond micromachining of symmetric waveguides at 1.5 µm by astigmatic beam focusing

We report on a new spatial beam-shaping approach for fabrication of waveguides with a circular transverse profile by femtosecond laser pulses, using an astigmatic beam and controlling both beam waist and focal position in the tangential and sagittal planes. We apply this technique to write single-mode active waveguides at 1.5microm in Er:Yb-doped glass substrates. The experimental results are well described by a simple nonlinear absorption model.

Optical waveguide writing with a diode-pumped femtosecond oscillator

Optical waveguide writing is demonstrated by means of a diode-pumped cavity-dumped Yb:glass femtosecond laser oscillator with a pulse energy of 270 nJ at a 166-kHz repetition rate. Waveguides realized on an Er:Yb-doped phosphate glass are almost perfectly mode matched to standard single-mode fibers at 1.55 microm and show a 1.2-dB net gain in a standard telecommunications amplifier setup. Waveguide writing with a compact femtosecond laser oscillator is an important step toward introducing this technique into an industrial context.

1.5 μm single longitudinal mode waveguide laser fabricated by femtosecond laser writing

A compact and efficient single longitudinal mode laser based on a femtosecond laser written waveguide is demonstrated. A maximum output power exceeding 50 mW was measured in single longitudinal and transverse mode operation, with 21% slope efficiency. The active waveguide was fabricated on erbium-ytterbium-doped phosphate glass by direct writing with femtosecond laser pulses from a diode-pumped cavity-dumped oscillator.

Intensity noise reduction in a single-frequency ytterbium-codoped erbium laser

We report on intensity noise suppression in a diode-pumped, single-frequency erbium bulk-glass laser codoped with ytterbium. Using an optoelectronic feedback circuit, we acheived a 30-dB reduction of the relaxation oscillation peak, at 160-kHz frequency, to a relative intensity noise of 2114 dByHz. A useful output power of 15 mW at 1533-nm wavelength was obtained.

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.

C-band waveguide amplifier produced by femtosecond laser writing

An optical waveguide amplifier fabricated on erbium-ytterbium-doped phosphate glass by direct femtosecond laser writing is demonstrated. The waveguides are manufactured using 1040-nm radiation from a diode-pumped cavity-dumped Yb:KYW oscillator, operating at a 885 kHz repetition rate, with a 350 fs pulse duration. Peak internal gain of 9.2 dB is obtained at 1535 nm, with a minimum internal gain of 5.2 dB at 1565 nm. Relatively low insertion losses of 1.9 dB enable for the first time an appreciable net gain in the full C-band of optical communications.

Active waveguide devices by Ag–Na ion exchange on erbium–ytterbium doped phosphate glasses

Abstract Arrays of buried channel waveguide lasers and amplifiers were fabricated by silver–sodium ion exchange in erbium–ytterbium doped phosphate glass substrates. The fabrication process, consisting of a thermal diffusion from fused salt followed by a field-assisted burial step, is optimized to get single-mode channel arrays fully compatible with standard single-mode fibres and fibre ribbon cables. The active channels were successfully tested realizing both lasers and amplifiers in the C-band suitable for optical communications. Erbium waveguide lasers exhibit a maximum output power of ∼1.7 mW and erbium-doped waveguide amplifiers provide a maximum internal gain of ∼11.3 dB at 1534 nm.

Spectroscopy of Er and Er–Yb-doped phosphate glasses

Abstract Optical absorption and emission properties of Er and Er–Yb-doped phosphate glasses are investigated both at low and room temperature in the near infrared spectral region between 800 and 2000 nm, and the results are thoroughly discussed in connection with the expected transitions originating from the crystal-field split 4 I 15/2 and 4 I 13/2 levels of the Er 3+ ion. Accurate measurements of the 4 I 13/2 fluorescence lifetimes and the determination of the stimulated emission cross section for the Er transition at 1.5 μm are also reported. Excited state absorption (ESA) from the metastable 4 I 13/2 level towards the higher energy levels is measured in the 450–1200 nm spectral region. The ESA absorption peaks are in good agreement with the positions of the higher states of the 4f 11 Er 3+ manifold.

Measurement of the energy transfer and upconversion constants in Er–Yb-doped phosphate glass

A simple method to measure the ytterbium-to-erbium energy transfer and the co-operative upconversion constants in a phosphate laser glass is proposed. The technique is based on the experimental acquisition of the luminescence decay from the Er3+ 4I13/2 metastable level at 1.5μm as a function of time and on a suitable fit of the experimental data. The fitting procedure relies on a simplified model of the Er–Yb system and makes use of a numerical solution of the rate equations to describe the dynamics of the populations, showing considerable sensitivity to the fitting parameters. The results obtained are in fairly good agreement with previous data reported in the literature.