A. E. H. Oehler

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.

1.55 µm InAs/GaAs Quantum Dots and High Repetition Rate Quantum Dot SESAM Mode-locked Laser

High pulse repetition rate (≥10 GHz) diode-pumped solid-state lasers, modelocked using semiconductor saturable absorber mirrors (SESAMs) are emerging as an enabling technology for high data rate coherent communication systems owing to their low noise and pulse-to-pulse optical phase-coherence. Quantum dot (QD) based SESAMs offer potential advantages to such laser systems in terms of reduced saturation fluence, broader bandwidth, and wavelength flexibility. Here, we describe the development of an epitaxial process for the realization of high optical quality 1.55 µm In(Ga)As QDs on GaAs substrates, their incorporation into a SESAM, and the realization of the first 10 GHz repetition rate QD-SESAM modelocked laser at 1.55 µm, exhibiting ∼2 ps pulse width from an Er-doped glass oscillator (ERGO). With a high areal dot density and strong light emission, this QD structure is a very promising candidate for many other applications, such as laser diodes, optical amplifiers, non-linear and photonic crystal based devices.

100 GHz passively mode-locked Er:Yb:glass laser at 1.5 µm with 1.6-ps pulses

We demonstrate a compact diode-pumped fundamentally modelocked Er:Yb:glass laser with a record high repetition rate of 101 GHz, generating 35 mW average power in 1.6-ps pulses in the 1.5-microm telecom window. This performance makes the laser an attractive pulse generator to be used in advanced high-speed return-to-zero (RZ) telecom systems.

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.

Timing Jitter Characterization of a Free-Running SESAM Mode-locked VECSEL

We present timing jitter measurements of an InGaAs quantum well vertical external cavity surface emitting laser (VECSEL) passively mode locked with a quantum dot semiconductor saturable absorber mirror (SESAM) at 2-GHz repetition rate. It generates 53-mW average output power in 4.6-ps pulses at 953 nm. The laser housing was optimized for high mechanical stability to reduce acoustic noise. We use a fiber-coupled multimode 808-nm pump diode, which is mounted inside the laser housing. No active cavity length stabilization is employed. The phase noise of the free-running laser integrated over a bandwidth from 100 Hz to 1 MHz corresponds to an RMS timing jitter of ≈212 fs, which is lower than previously obtained for mode-locked VECSELs. This clearly confirms the superior noise performance expected from a high-Q-cavity semiconductor laser. In contrast to edge-emitting semiconductor diode lasers, the cavity mode is perpendicular to the quantum well gain layers, which minimizes complex dispersion and nonlinear dynamics.

Broad multiwavelength source with 50 GHz channel spacing for wavelength division multiplexing applications in the telecom C band

We present a multiwavelength source with a spectral width of 42 nm at -20 dB. The frequency comb is generated by spectrally broadening the output of an amplified 50 GHz Er:Yb:glass laser with a highly nonlinear photonic crystal fiber. After spectral flattening the comb covers 37 channels with 5.4 mW average power per channel, and locking only one central wavelength channel to the International Telecommunication Union grid results in a maximum frequency error of 0.24% for all channels.

High Throughput and High Precision Laser Micromachining with ps-Pulses in Synchronized Mode with a fast Polygon Line Scanner

To be competitive in laser micro machining, high throughput is an important aspect. One possibility to increase productivity is scaling up the ablation process i.e. linearly increasing the laser repetition rate together with the average power and the scan speed. In the MHz-regime high scan speeds are required which cannot be provided by commercially available galvo scanners. In this work we will report on the results by using a polygon line scanner having a maximum scan speed of 100 m/s and a 50 W ps-laser system, synchronized via the SuperSync™ technology. We will show the results concerning the removal rate and the surface quality for working at the optimum point i.e. most efficient point at repetition rates up to 8.2 MHz.

Multi-Wavelength Laser Source for Dense Wavelength Division Multiplexing Networks

We propose and demonstrate an ITU-T grid compatible DWDM laser source with 50 GHz channel spacing. It consists of a passively mode-locked laser, supercontinuum-generating photonic crystal fiber and fiber Fabry-Perot filter for spectral selection.

High throughput surface structuring with ultrashort pulses in synchronized mode with fast polygon line scanner

High precision laser micromachining requires an exact synchronization of the laser pulse train with the mechanical axes of the motion system to ensure for each single pulse a precise control of the laser spot position - on the target. For ultra short pulsed laser systems this was already demonstrated with a conventional two-axis galvanometer scanner. But this solution is limited by the scanner architecture to a marking speed of about 10m/s with a maximum scan line length of about 100mm. It is therefore not suited for average powers far beyond 10W when working at the optimum point with highest removal rate and machining quality is desired. A way to overcome this limitation is offered by polygon line scanners which are able to realize much higher lateral speeds at large scan line lengths.In this work we will report on the results with a polygon line scanner having a maximum moving spot velocity of 100m/s, a scan line length of 170mm, spot diameters of 45µm (1064nm) and 22µm (532nm) together with a 50W, 10-ps laser system. The precise control of the laser spot position i.e. the synchronization is realized via the new SuperSyncTM technology. Decoating, perforation and 3D patterning will act as benchmark processes to evaluate this scanning technology.High precision laser micromachining requires an exact synchronization of the laser pulse train with the mechanical axes of the motion system to ensure for each single pulse a precise control of the laser spot position - on the target. For ultra short pulsed laser systems this was already demonstrated with a conventional two-axis galvanometer scanner. But this solution is limited by the scanner architecture to a marking speed of about 10m/s with a maximum scan line length of about 100mm. It is therefore not suited for average powers far beyond 10W when working at the optimum point with highest removal rate and machining quality is desired. A way to overcome this limitation is offered by polygon line scanners which are able to realize much higher lateral speeds at large scan line lengths.In this work we will report on the results with a polygon line scanner having a maximum moving spot velocity of 100m/s, a scan line length of 170mm, spot diameters of 45µm (1064nm) and 22µm (532nm) together with a 50W, 10-p...

10 GHz pulse repetition rate Er:Yb:glass laser modelocked with quantum dot semiconductor saturable absorber mirror.

Semiconductor saturable absorber mirror (SESAM) modelocked high pulse repetition rate (≥10  GHz) diode-pumped solid-state lasers are proven as an enabling technology for high data rate coherent communication systems owing to their low noise and high pulse-to-pulse optical phase-coherence. Compared to quantum well, quantum dot (QD)-based SESAMs offer potential advantages to such laser systems in terms of reduced saturation fluence, broader bandwidth, and wavelength flexibility. Here, we describe the first 10 GHz pulse repetition rate QD-SESAM modelocked laser at 1.55 μm, exhibiting 2 ps pulse width from an Er-doped glass oscillator (ERGO). The 10 GHz ERGO laser is modelocked with InAs/GaAs QD-SESAM with saturation fluence as low as 9  μJ/cm2.