We describe unprecedented performance level from a femtosecond fiber laser system optimized for precision industrial micro-machining. The monolithic fiber chirped pulse amplifier chain enables system output of 215 μJ pulse energy, ~510 fs pulse duration and 16 W average power. We reveal the critical enabling technology to reach this unprecedented pulse energy level, the salient operating principles for the full chirped pulse amplification system, and the key experimental performance data for the laser system.
Ultrashort pulse lasers based on fiber optic architecture will play a dominant role in the spread of these lasers into research and industrial applications. The principle challenge is to generate adequate pulse energy from singlemode or quasi-singlemode amplifiers which have small cross-sectional area. We demonstrate a robust, all-fiber erbium amplifier system that produces >100 μJ per pulse with 701 fs pulsewidth and M2 < 1.3. We will discuss the salient amplifier dynamics that influence the pulse generation, shaping, and propagation phenomena in state-of-the-art erbium fiber lasers. Furthermore, we show data relevant to applications and implementation of ultrashort pulse lasers.
Despite the growing number of biomedical and micromachining applications enabled by ultra-short pulse lasers in
laboratory environments, realworld applications remain scarce due to the lack of robust, affordable and flexible laser
sources with meaningful energy and average power specifications. In this presentation, we will describe a laser source
developed at the eye-safe wavelength of 1552.5 nm around a software architecture that enables complete autonomous
control of the system, fast warm-up and flexible operation. Our current desktop ultra-short pulse laser system offers
specifications (1-5 microJ at 500 kHz, 800 fs-3 ps pulse width, variable repetition rate from 1 Hz to 500 kHz) that are
meaningful for many applications ranging from medical to micromachining. We will also present an overview of
applications that benefit from the range of parameters provided by our desktop platform. Finally, we will present a novel
scalable approach for fiber delivery of high peak power pulses using a hollow core Bragg fiber recently developed for
the first time by Raydiance and the Massachusetts Institute of Technology for operation around 1550 nm. We will
demonstrate that this fiber supports single mode operation for core sizes up to 100 micron, low dispersion and low
nonlinearities with acceptable losses. This fiber is a good candidate for flexible delivery of ultra-short laser pulses in
applications such as minimally accessible surgery or remote detection.
Spectrally resolved interferometry combining up-chirped and down-chirped pulses allows for millimeter range
resolution in laser ranging applications. Key in our approach is the use of temporally stretched optical pulses of 5
nanoseconds in duration. These stretched pulses were obtained from a femtosecond semiconductor mode-locked laser
and were up-chirped and down-chirped using a chirped fiber Bragg grating and recombined to realize spectral
interferometry. This approach provides a means to achieve the high pulse energies required for a laser radar application
which are easy to achieve using nanosecond pulses but maintains the high spatial resolution associated with
femtosecond optical pulses.
A proposed method, called "eXtreme Chirped Pulse Amplification(X-CPA)", to overcome the limitation of small storage energy of semiconductor optical amplifiers is demonstrated experimentally and theoretically. Results show an efficient energy extraction, a nonlinear suppression, and an excellent optical signal-to-noise ratio. In addition, we built an all-semiconductor X-CPA system using a highly dispersive chirped fiber Bragg grating which possesses 1600ps/nm with 6nm bandwidth at 975nm which generates sub-picosecond optical pulses with >kW record peak power output at 95MHz.
A hybridly modelocked grating-coupled surface-emitting laser (GCSEL) with pulse duration 2.8psec at 980nm is demonstrated. The unpumped grating section of the GCSEL is used as a saturable absorber to generate pulses with a 535MHz repetition rate. The peak power of 0.31W and a spectral bandwidth of 1.1nm are obtained.
We demonstrate an external cavity, active mode-locked GCSEL. The optical pulse duration from the actively mode-locked oscillator is 22.6ps and a 3 dB optical spectrum bandwidth is 0.07nm at 976nm. The average power from the oscillator is 0.72mW and its peak power is 108mW. The amplification characteristics of a GCSOA, optically injected with a continuously operated external cavity GCSEL, are also demonstrated. Despite the observation of lasing from the device, injection locking can be performed using an external source. At 4A peak current injection, 375mW output is achieved with 12mW injection.