Philippe Bado

Generation of ultrahigh peak power pulses by chirped pulse amplification

Single picosecond pulses have been amplified to the terawatt level by a table-top-size Nd:glass amplifier by using the technique of chirped pulse amplification (CPA). The divergence of the beam is twice the diffraction limit, making the brightness of this source equal to approximately 2*10/sup +18/ W/(cm-sr), which is thought to be the highest brightness yet reported. The CPA technique allows the efficient energy extraction from extremely compact amplifier systems. Amplification of chirped pulses over nine orders of magnitude, i.e. from nanojoule to the joule level, has been demonstrated. >

Nd:YLF mode-locked oscillator and regenerative amplifier

Pulses of 37-psec duration are generated by a cw actively mode-locked Nd:YLF oscillator and subsequently amplified to 2.5 mJ in a cw-pumped Nd:YLF regenerative amplifier operating at a repetition rate of 500 Hz. In comparison, the same system refitted with Nd:YAG gain media produces longer pulses (~80 psec) with lower energy (1 mJ).

Kilohertz synchronous amplification of 85-femtosecond optical pulses

High-repetition-rate laser pulse amplifiers are desirable for investigations of weak signals because of the ability to use ultrasensitive lock-in detection. We have developed a new oscillator and amplifier capable of providing 10 MW of power at repetition rates in excess of 1 kHz. By focusing this pulse we have obtained the white-light continuum with as little as 250 nJ of energy.

Chirped pulse amplification of 300 fs pulses in an alexandrite regenerative amplifier

The amplification of femtosecond dye laser pulses up to the 3.5-mJ level in an alexandrite regenerative amplifier is discussed. An expansion/compression system using diffraction gratings allows chirped amplification techniques to be used to produce peak powers upwards of 1 GW. Limitations in the chirped pulse amplification of ultrashort pulses due to intracavity dispersive elements are discussed. >

Waveguide electro-optic modulator in fused silica fabricated by femtosecond laser direct writing and thermal poling

An integrated electro-optic waveguide modulator is demonstrated in bulk fused silica. A Mach-Zehnder interferometer waveguide structure is fabricated by direct writing with a femtosecond laser followed by thermal poling. A 20 degrees electro-optic phase shift is achieved at an operating wavelength of 1.55 microm with an applied voltage of 400 V and an interaction length of 25.6 mm, which correspond to an estimated effective electro-optic coefficient of 0.17 pm/V for the TE-polarized mode.

Regenerative amplification of picosecond pulses in Nd:YLF: gain narrowing and gain saturation

The effects of gain narrowing and gain saturation in the regenerative amplification of frequency-chirped picosecond pulses are examined by using a Nd:YLF-based laser system.

Wavelength tunable alexandrite regenerative amplifier

We describe a wavelength tunable alexandrite regenerative amplifier which is used to amplify nanosecond slices from a single-frequency cw dye laser or 50-ps pulses emitted by a diode laser to energies in the 10-mJ range. The amplified 5-ns slices generated by the cw-pumped line narrowed dye laser are Fourier transform limited. The 50-ps pulses emitted by a gain-switched diode laser are amplified by more than 10 orders of magnitude in a single stage.

Fabrication and characterization of microstructures with optical quality surfaces in fused silica glass using femtosecond laser pulses and chemical etching

We present a study of the sidewall surface quality inside microchannels fabricated in fused silica glass by femtosecond laser pulses and chemical etching. Multiple combinations of laser exposure and etching solution parameters were examined. Results of scanning electron microscopy, atomic force microscopy, and optical reflection analyses of the surfaces are presented. The results obtained demonstrate the feasibility of optical quality surface fabrication, which in turn demonstrates the feasibility of fabricating complex integrated devices containing microfluidic channels and optical waveguides in the glass substrates.

Regenerative amplification in alexandrite of pulses from specialized oscillators

An alexandrite regenerative amplifier, used to amplify the output of various specialized oscillators, is described. Nanosecond pulses from a narrow-frequency CW-pumped dye laser, picosecond pulses from a gain-switched diode laser, and femtosecond pulses from a synchronously pumped dye laser were amplified by 6-10 orders of magnitude in a single stage while conserving the temporal and spectral profiles characteristic to the oscillators. >

In-situ optical detection of mesoscale components in glass microfluidic channel with monolithic waveguide

Optical waveguides used as a local light source along a fluidic channel have proven to be an effective approach to detecting cells in the field of flow-cytometry. One challenge, however, has been a simple integration of optical waveguides with the fluidic channel. We employ the use of femtosecond laser-writing process to pattern a waveguide in the bulk of a fused-silica glass substrate housing a fluidic channel. We demonstrate an in-situ scheme for detecting sub-millimeter components based on such a monolithically fabricated device. By illuminating the waveguide and collecting the light signal past the channel, we detect opaque and transparent components between 300 - 500 μm in size, as each moves along the channel. Both an opaque square chip and a transparent bead attentuate the signal by more than 95% primarily due to reflection and refraction respectively. The signature of a transparent bead additionally shows attenuated peaks which we attribute to normal incidence of light from the waveguide. The projected sizes of the parts are determined with less than 1% uncertainty. We conclude that the femtosecond laser produced waveguides in fused-silica glass are a viable option for the detection of certain kinds of sub-millimeter components. This approach holds the prospects of fabricating complex three-dimensional networks of waveguides monolithically.