Selina Pekarek

Diode-pumped gigahertz femtosecond Yb:KGW laser with a peak power of 3.9 kW

We present a diode-pumped Yb:KGW laser with a repetition rate of 1 GHz and a pulse duration of 281 fs at a wavelength of 1041 nm. A high brightness distributed Bragg reflector tapered diode laser is used as a pump source. Stable soliton modelocking is achieved with a semiconductor saturable absorber mirror (SESAM). The obtained average output power is 1.1 W and corresponds to a peak power of 3.9 kW and a pulse energy of 1.1 nJ. With harmonic modelocking we could increase the pulse repetition rate up to 4 GHz with an average power of 900 mW and a pulse duration of 290 fs. This Yb:KGW laser has a high potential for stable frequency comb generation.

Self-referenceable frequency comb from a gigahertz diode-pumped solid-state laser

We present carrier envelope offset (CEO) frequency detection of a diode-pumped Yb:KGW (ytterbium-doped potassium gadolinium tungstate) laser with a repetition rate of 1 GHz. The SESAM-soliton-modelocked laser delivers 2.2-W average power in 290-fs pulses. This corresponds to a peak power of 6.7 kW and the optical-to-optical efficiency is 38%. With a passive pulse compression the duration is reduced to 100 fs at an average power of 1.1 W. Coherent supercontinuum (SC) generation in a highly nonlinear photonic crystal fiber (PCF) is achieved without additional amplification. Furthermore we have demonstrated that pulse compression towards lower soliton orders of approximately 10 was required for coherent SC generation and CEO detection. Additional numerical simulations further confirm these experimental results.

Self-referenceable frequency comb from an ultrafast thin disk laser

We present the first measurement of the carrier envelope offset (CEO) frequency of an ultrafast thin disk laser (TDL). The TDL used for this proof-of-principle experiment was based on the gain material Yb:Lu(2)O(3) and delivered 7 W of average power in 142-fs pulses, which is more than two times shorter than previously realized with this material. Using only 65 mW of the output of the laser, we generated a coherent octave-spanning supercontinuum (SC) in a highly nonlinear photonic crystal fiber (PCF). We detected the CEO beat signal using a standard f-to-2f interferometer, achieving a signal-to-noise ratio of >25 dB (3 kHz resolution bandwidth). The CEO frequency was tunable with the pump current with a slope of 33 kHz/mA. This result opens the door towards high-power frequency combs from unamplified oscillators. Furthermore, it confirms the suitability of these sources for future intralaser extreme nonlinear optics experiments such as high harmonic generation and VUV frequency comb generation from compact sources.

Fully stabilized optical frequency comb with sub-radian CEO phase noise from a SESAM-modelocked 1.5-µm solid-state laser

We report the first full stabilization of an optical frequency comb generated from a femtosecond diode-pumped solid-state laser (DPSSL) operating in the 1.5-μm spectral region. The stability of the comb is characterized in free-running and in phase-locked operation by measuring the noise properties of the carrier-envelope offset (CEO) beat, of the repetition rate, and of a comb line at 1558 nm. The high Q-factor of the semiconductor saturable absorber mirror (SESAM)-modelocked 1.5-µm DPSSL results in a low-noise CEO-beat, for which a tight phase lock can be much more easily realized than for a fiber comb. Using a moderate feedback bandwidth of only 5.5 kHz, we achieved a residual integrated phase noise of 0.72 rad rms for the locked CEO, which is one of the smallest values reported for a frequency comb system operating in this spectral region. The fractional frequency stability of the CEO-beat is 20‑fold better than measured in a standard self-referenced commercial fiber comb system and contributes only 10(-15) to the optical carrier frequency instability at 1 s averaging time.

Femtosecond diode-pumped solid-state laser with a repetition rate of 4.8 GHz.

We report on a diode-pumped Yb:KGW (ytterbium-doped potassium gadolinium tungstate) laser with a repetition rate of 4.8 GHz and a pulse duration of 396 fs. Stable fundamental modelocking is achieved with a semiconductor saturable absorber mirror (SESAM). The average output power of this compact diode-pumped solid state laser is 1.9 W which corresponds to a peak power of 0.9 kW and the optical-to-optical efficiency is 36%. To the best of our knowledge, this is the femtosecond DPSSL with the highest repetition rate ever reported so far.

High-brightness distributed-Bragg-reflector tapered diode lasers: pushing your application to the next level

We demonstrate monolithic distributed-Bragg-reflector tapered diode lasers having an output power up to 12 W, a small spectral width of below ▵λ<10 pm and a beam quality close to the diffraction limit. This results in a brightness close to 1 GWcm-2sr-1. Due to these excellent electro-optical characteristics we achieved visible laser light up to P=1.8 W in a single-path second harmonic generation experiment. This allowed us to develop compact Watt-class (P=1.1 W) visible laser modules having an excellent beam quality (M²<3) with a narrow spectrum (▵λ<30 pm). The entire device is integrated on a micro-optical bench with a volume below 20 cm³. In another application we demonstrate for the first time a femtosecond gigahertz SESAM-modelocked Yb:KGW laser. Such a laser system benefits from the small spectral emission and the focusability of the developed diode laser. A record peak power of 3.9 kW was achived. At the repetition rate of 1 GHz, 281 fs pulses with an average output power of 1.1 W were generated. This Yb:KGW laser has a high potential for stable frequency comb generation.

Ultrafast thin disk lasers: Towards intralaser extreme nonlinear optics

Ultrafast thin disk lasers generate higher power levels than any other femtosecond oscillator technology. We review the current state of the art and give an outlook towards new applications such as intralaser extreme nonlinear optics.

Compact Gigahertz Frequency Comb Generation: How Short Do The Pulses Need To Be?

We investigate the required pulse duration for coherent supercontinuum generation for CEO detection in the 1-µm and 1.5-µm spectral regime. We demonstrate the first self-referenceable frequency comb from a gigahertz diode-pumped solid state laser.

Self-referenceable High-power Frequency Comb from a 7-W, 142-fs Yb:Lu2O3 Thin Disk Laser Oscillator

We present an Yb:Lu2O3 modelocked thin disk laser (TDL) with 7W and record short pulse duration of 142fs. Using 65mW we generated an octave spanning supercontinuum and measured for the first time the carrier envelope offset (CEO) frequency of a TDL.

First fully stabilized frequency comb from a SESAM-modelocked 1.5-µm solid-state oscillator

In conclusion, we have demonstrated the first fully stabilized frequency comb generated by an ultrafast Er:Vb:glass laser. The SESAM-modelocked, diode-pumped laser uses a high-Q cavity which results in low-noise operation. A coherent, octave-spanning SC is generated by nonlinear spectral broadening in a polarization maintaining highlynonlinear fiber. We observe a more than 10-times improvement in the free-running CEO frequency linewidth compared to free-running femtosecond fiber laser systems operating in this spectral region. The CEO frequency and the repetition rate are stabilized to the same 10-MHz external reference over hours. The Allan deviation of the 20-MHz CEO reaches 10-8 at 1-s with an H-maser as an external reference and a stable locked operation of more than 11 hours was achieved in a preliminary long-term evaluation. A CEO-beat signal can still be observed at a large reduction of the pump power, resulting in a reduced intracavity pulse energy and in an increased pulse duration up to 260 fs. We expect that this result will have a significant impact for the future development of more compact stable frequency combs as the relatively long pulse duration relaxes the requirements on the modelocked laser. This will become even more important for gigahertz pulse repetition rates.