Kyungbum Kim

Monolithic fiber chirped pulse amplification system for millijoule femtosecond pulse generation at 1.55 µm

A monolithic fiber chirped pulse amplification system that generates sub-500 fs pulses with 913 µJ pulse energy and 4.4 W average power at 1.55 µm wavelength has recently been demonstrated. The estimated peak power for the system output approached 1.9 GW. The pulses were near diffraction-limited and near transform-limited, benefiting from the straight and short length of the booster amplifier as well as adaptive phase shaping for the overall mitigation of the nonlinear phase accumulation. The booster amplifier employs an Er(3+)-doped large mode area high efficiency media fiber just 28 cm in length with a fundamental mode (LP(01)) diameter of 54 µm and a corresponding effective mode area of 2290 µm(2).

Higher-order mode fiber enables high energy chirped-pulse amplification

Energy scaling of femtosecond fiber lasers has been constrained by nonlinear impairments and optical fiber damage. Reducing the optical irradiance inside the fiber by increasing mode size lowers these effects. Using an erbium-doped higher-order mode fiber with 6000 µm(2) effective area and output fundamental mode re-conversion, we show a breakthrough in pulse energy from a monolithic fiber chirped pulse amplification system using higher-order mode propagation generating 300 µJ pulses with duration <500 fs (FWHM) and peak power >600 MW at 1.55 µm. The erbium-doped HOM fiber has both a record large effective mode area and excellent mode stability, even when coiled to reasonable diameter. This demonstration proves efficacy of a new path for high energy monolithic fiber-optic femtosecond laser systems.

Monolithic polarization maintaining fiber chirped pulse amplification (CPA) System for high energy femtosecond pulse generation at 1.03 µm

A monolithic polarization maintaining fiber chirped pulse amplification system with 25 cm Yb(3+)-doped high efficiency media fiber that generates 62 µJ sub-400 fs pulses with 25 W at 1.03 µm has recently been demonstrated.

Pulse and amplifier dynamics in high energy fiber optic ultrashort pulse laser systems

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.

215 μJ, 16 W femtosecond fiber laser for precision industrial micro-machining

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.

Monolithic Polarization Maintaining Fiber Chirped Pulse Amplification System for High Energy Femtosecond Pulse Generation at 1.03 µm

A monolithic polarization maintaining fiber chirped pulse amplification system with 30 cm Yb3+-doped high efficiency media fiber that generates 25 µJ sub-500 fs pulses with 20 W at 1.03 µm has recently been demonstrated.

High energy ultrafast fiber laser systems and their application to high quality medical device processing

Ultrafast lasers based on fiber optic architecture and integrated software controls will play a dominant role in the spread of these lasers into commercial and industrial applications. The principle challenges are to generate adequate pulse energy from singlemode fiber amplifiers, which have small cross-sectional area, and to perform all tuning and control processes with embedded electronics and robust software. We demonstrate an all-fiber erbium amplifier system that produces >100 µJ per pulse with femtosecond class pulsewidth, excellent beam quality, and an autonomous control system. We present details regarding our laser platform micromachining performance with specific focus on innovative medical device manufacturing. As example, we show processing of relevant metal alloys and dielectrics without burrs, slag, or heat affected zone. Hence fewer post-processing steps are needed during device fabrication. We also discuss the salient reliability and lifetime topics that are necessary for ultrafast lasers to spread into realistic industrial environments.Ultrafast lasers based on fiber optic architecture and integrated software controls will play a dominant role in the spread of these lasers into commercial and industrial applications. The principle challenges are to generate adequate pulse energy from singlemode fiber amplifiers, which have small cross-sectional area, and to perform all tuning and control processes with embedded electronics and robust software. We demonstrate an all-fiber erbium amplifier system that produces >100 µJ per pulse with femtosecond class pulsewidth, excellent beam quality, and an autonomous control system. We present details regarding our laser platform micromachining performance with specific focus on innovative medical device manufacturing. As example, we show processing of relevant metal alloys and dielectrics without burrs, slag, or heat affected zone. Hence fewer post-processing steps are needed during device fabrication. We also discuss the salient reliability and lifetime topics that are necessary for ultrafast lasers ...

Autonomous, flexible and reliable ultra-short pulse laser at 1552.5 nm

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.