Daniel Jedrzejczyk

High peak power optical pulses generated with a monolithic master-oscillator power amplifier

We present results on a monolithic semiconductor-based master-oscillator power amplifier (MOPA) combining a distributed-feedback (DFB) laser and a tapered amplifier on a single chip. The MOPA reaches an output power of almost 12 W at an emission wavelength around 1064 nm in continuous-wave operation. Pulses with a length of around 100 ps can be obtained either by injecting nanosecond current pulses into the tapered amplifier alone or into both the DFB laser and the tapered amplifier. In the latter case, pulses with a width of 84 ps, a peak power of 42 W, and a spectral width of 160 pm are generated.

Second-harmonic-generation microsystem light source at 488 nm for Raman spectroscopy

A microsystem excitation light source emitting at 488 nm is presented. A direct single-pass nonlinear frequency conversion using a diode laser emission at 976 nm and a periodically poled lithium niobate waveguide crystal for efficient second-harmonic generation is demonstrated. This was realized on a micro-optical bench with a combined thermal management and a footprint of (25 mm x 5 mm). At 217 mW fundamental power a generated power of 56 mW at 488 nm with a conversion efficiency of 26% was achieved. With a power stability below 1%, this wavelength stabilized compact device is well suited for Raman spectroscopy.

Efficient high-power frequency doubling of distributed Bragg reflector tapered laser radiation in a periodically poled MgO-doped lithium niobate planar waveguide

We report on efficient single-pass, high-power second-harmonic generation in a periodically poled MgO-doped LiNbO3 planar waveguide using a distributed Bragg reflector tapered diode laser as a pump source. A coupling efficiency into the planar waveguide of 73% was realized, and 1.07 W of visible laser light at 532 nm was generated. Corresponding optical and electro-optical conversion efficiencies of 26% and 8.4%, respectively, were achieved. Good agreement between the experimental data and the theoretical predictions was observed.

Watt-level second-harmonic generation at 589 nm with a PPMgO:LN ridge waveguide crystal pumped by a DBR tapered diode laser.

A DBR tapered diode laser in continuous wave operation was used to generate second-harmonic radiation at 589 nm in a PPMgO:LN ridge waveguide crystal. An optical output power of 0.86 W at an optical-to-optical and an electrical-to-optical efficiency of 42% and 11%, respectively, was achieved. The visible radiation was characterized by a spectral bandwidth ΔνFWHM of 230 MHz and a beam propagation parameter M1/e22 better than 1.1. The integration of such a system into a housing of a small footprint will enable a portable and highly efficient module featuring a visible output power in the watt-level range.

High-power distributed-feedback tapered master-oscillator power amplifiers emitting at 1064 nm

In this work, we investigate experimentally optimized monolithic distributed-feedback (DFB) tapered master-oscillator power amplifiers (MOPA). The devices consist of three autonomously driven sections: a 1 mm long DFB ridgewaveguide (RW) laser, a 1 mm long RW pre-amplifier and 2 mm or 4 mm long tapered amplifiers. The ridge width and the full taper angle are 5 μm and 6°, respectively. Both laser facets are anti-reflection coated. The second order Bragg gratings in the DFB laser were realized by holographic photolithography, wet-chemical etching and a two-step epitaxy. The DFB tapered MOPAs emit nearly diffraction limited spectral single mode CW radiation at 1064 nm. The 6 mm long devices provide an optical power of about 12 W at DFB laser, pre-amplifier and tapered amplifier currents of 150 mA, 400 mA and 18 A, respectively. The 4 mm long devices generate more than 4 W at a tapered amplifier current of 7 A. The spectral drift versus output power is below 50 pm/W.

High-power (1.1W) green (532nm) laser source based on single-pass second harmonic generation on a compact micro-optical bench

We demonstrate a compact high-power green (532nm) laser module based on single-pass second harmonic generation. The pump source is a distributed Bragg reflector tapered diode laser. The frequency conversion is achieved with a 2.5 cm long periodically poled MgO:LiNbO3 bulk crystal. The entire module is integrated on a compact micro-optical bench with a footprint of 2.5 cm3. Up to 1.1 W output green light power is achieved at a pump power of 7.6 W with an optical conversion efficiency of about 15% and a corresponding module wall-plug efficiency of more than 4%. The green laser beam has a relatively good beam quality (measured at output power level of ~0.9 W) with M²σ=1.8 in the vertical direction and M²=4.9 in the lateral direction, respectively. The long-term output power stability is ±10% (tested at output power level of ~0.6 W).

Second harmonic pico-second pulse generation with mode-locked 1064nm DBR laser diodes

Detailed experimental investigations of the generation of high-energy short infrared and green pulses with a mode-locked multi-section distributed Bragg reflector (DBR) laser in dependence on the lengths of the gain section and the saturableabsorber (SA) section as well the corresponding input currents and reverse voltages, respectively, are presented. The laser under investigation is 3.5 mm long and has a 500 μm long DBR section. The remaining cavity was divided into four 50 μm, four 100 μm, two 200 μm and eight 250 μm long electrically separated segments so that the lengths of the gain and SA sections can be simply varied by bonding. Thus, the dependence of the mode-locking behavior on the lengths of the gain and SA sections can be investigated on the same device. Optimal mode-locking was obtained for absorber lengths between LAbs = 200 μm and 300 μm and absorber voltages between UAbs= -2 V and -3 V. A pulse length of τ ≈ 10 ps, a repetition frequency of 13 GHz and a RF line width of less than 100 kHz were measured. An infrared peak pulse power of 900 mW was reached. The FWHM of the optical spectrum was about 150 pm. With an 11.5 mm long periodically poled MgO doped LiNbO3 crystal having a ridge geometry of 5 μm width and 4 μm height green light pulses were generated. With an infrared pump peak power of 900 mW a green pulse energy of 3.15 pJ was reached. The opto-optical conversion efficiency was about 31%.

Compact Blue Light Source by Single-Pass Second Harmonic Generation of DBR Tapered Laser Radiation

We demonstrate a continuous-wave 460-nm compact visible laser module having a footprint of 75 mm × 25 mm × 25 mm. This blue light source is achieved through single-pass second harmonic generation with a distributed Bragg reflector tapered diode laser as a single-frequency pump source at ~920 nm in a periodically poled MgO-doped lithium niobate crystal with a planar waveguide. The compact blue laser module reached an optical output power of 286 mW with the highest optical conversion efficiency of 11.6% at room temperature. The power stability of the blue light from the laser module is measured at an output power of 268 mW with a variation of ±3.5% during a period of 1 h.

High-Power Single-Mode Fiber Coupling of a Laterally Tapered Single-Frequency Diode Laser

In this letter, we investigate experimentally single-mode fiber (SMF) coupling of a nondiffraction limited, astigmatic beam generated by a near-infrared distributed Bragg reflector tapered diode laser at high output powers. In particular, a systematic study of the coupling efficiency as well as spectral and spatial laser beam characteristics behind the SMF is carried out in dependence on the properties of the collimated beams in front of the SMF, which are generated at given operating points of the diode laser. A stigmatic, nearly Gaussian laser beam is obtained behind the SMF independent on the diode laser operating point and the input optical power. A maximum power of 3.5 W ex fiber at a power coupling efficiency of 65% is reached.

Miniaturized laser amplifier modules for wavelengths of 1180 nm with PM-fiber input and more than 1 W optical output power

In this paper a micro-integrated laser-amplifier for a wavelength of 1180nm is presented. The modules can amplify laser emission from any source, which is coupled into the polarization-maintaining input fiber of the module, to an optical power > 1W. Thereby, the spectral properties of the seed source are maintained. The output of the module is free space allowing easy access to the emitted beam. The footprint of the module is only 47mm • 34 mm. The article discusses the utilized amplifiers, preceding bench top experiments and gives a detailed experimental characterization of the amplifier module.