Single Laser Oscillator Research Articles

Stable evanescent wave mode-locked laser based on a photonic-crystal-fiber-induced Mach-Zehnder filter as a gain-tilt equalizer.

In this paper, a switchable multichannel ytterbium-doped fiber laser based on a Mach-Zehnder interferometer (MZI) has been experimentally demonstrated. The MZI is fabricated by splicing a short piece of nonlinear photonic-crystal fiber (NLPCF) between two segments of a single-mode fiber. MZI-based NLPCF gathering with the intracavity birefringence polarization controller offers functions as both the selective comb filter and the mode locker. The laser can emit a single, dual, triple, or quadruple channel that can be varied in the spectral span around1030-1050 nm by only adjusting the pump power or polarization state. A stable evanescent wave, picosecond mode-locking generation with variable repetition rate (24.5 to 18.23 MHz and 34.64 MHz) has been realized via only inserting the polarization controller and adjusting its state inside the cavity. To the best of the authors' knowledge, this the first demonstration of a passive filter based on a NLPCF-MZ interferometer to generate switchable mode-locked pulses delivered from a single laser oscillator.

Independently tunable dual-wavelength fiber oscillator with synchronized pulsed emission based on a theta ring cavity and a fiber Bragg grating array.

We present a fiber-integrated laser enabling independent tuning of two emission wavelengths with a synchronized pulsed emission. The discrete tuning concept comprises a theta cavity fiber laser (TCFL), a fiber Bragg grating (FBG) array as a versatile spectral filter, facilitating tailored tuning ranges, and optical gating to control the emission spectrum. A novel electrical driving scheme uniquely enables independently tunable multi-wavelength emission from a single laser oscillator. Tunable dual-wavelength emission is experimentally investigated with a ytterbium (Yb)-doped TCFL using an FBG array with 11 gratings. Over a tuning range of 25 nm, 55 wavelength pairs have been demonstrated with high signal contrast (≈ 40 dB) and narrow linewidth (< 40GHz). Based on the demands of prospective applications, pulse synchronicity is studied with a fiber-based time-delay spectrometer (TDS) simultaneously measuring the joint temporal and spectral pulse properties down to a single-pulse analysis. Accordingly, tunable and fully synchronized dual-wavelength emissions have been verified by driving the TCFL with optimized electrical gating parameters. This unique operation mode achieved in a cost-efficient fiber-integrated laser design targets novel applications e.g. in nonlinear spectroscopy and biophotonics.

Fiber-format stimulated-Raman-scattering microscopy from a single laser oscillator

A highly simplified architecture for stimulated-Raman-scattering microscopy is demonstrated, where multiple tunable narrowband picosecond pulses are generated by spectral compression of femtosecond pulses emitted by a single compact Er-fiber oscillator. The system provides high sensitivity (2x10(-7)) and spectral resolution (sub-15 cm(-1)), and it offers an unprecedented flexibility for multicolor imaging.

Fiber-format CARS spectroscopy by spectral compression of femtosecond pulses from a single laser oscillator

We demonstrate an approach to coherent anti-Stokes Raman scattering (CARS) spectroscopy/microscopy based on spectral compression of femtosecond pulses emitted by a compact Er-fiber oscillator. Spectral compression is achieved by group-velocity mismatched second-harmonic generation in periodically poled nonlinear crystals, and it allows efficient synthesis of synchronized narrow-bandwidth (less than 10 cm(-1)) pump and Stokes pulses with the frequency difference continuously tunable up to approximately 3000 cm(-1). CARS signal enhancement by up to 3 orders of magnitude is obtained by interferometric superposition with a phase-coherent local oscillator field, also synthesized by spectral compression.

Powerful red-green-blue laser source pumped with a mode-locked thin disk laser.

We present a red-green-blue laser source with average powers of 8 W in the red, 23 W in the green, and 10.1 W in the blue. The entire pump power for the nonlinear conversion stages is provided by a single laser oscillator without any amplifier stages. Our system does not require any synchronized cavities, and all nonlinear crystals except one are critically phase matched at room temperature.

Simultaneous multiwavelength generation from a mode-locked all-solid-state Cr:forsterite laser

We demonstrate a multiple-channel, mode-locked, all-solid-state Cr:forsterite laser. By inserting an etalon into the laser cavity, we have generated 12 phase-locked channels with 9-19-ps pulse width near 1230 nm with 280-mW average output power from a single laser oscillator. By tuning the etalon bandwidth we can shorten the pulse width in a specific channel to 1.8 ps.

Spectral filtering of femtosecond laser pulses by interference filters

Phase properties of optical thin film interference filters are discussed from the aspect of their usage for phase-error free wavelength separation of broadband femtosecond laser pulses. It is shown that both transmissive or reflective interference filters with high contrast ratios exhibit high cubic phase shifts on transmission or reflection, respectively, causing intolerable distortion in the temporal pulse shape. We show, however, that high efficiency wavelength separation of broadband femtosecond laser pulses can be achieved by using low contrast, properly designed reflective optical interference filters directly built into the cavity of the broad spectrum, femtosecond pulse lasers or parametric oscillators. For demonstrative purposes, we implemented the idea for a Kerr-lens mode-locked Ti:sapphire laser, and obtained two-color, inherently synchronized, unchirped, femtosecond pulse outputs from a single laser oscillator.