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The electrical circuit of the jumping ring experiment based on discharging a capacitor is optimized. The setup is scoop proof at 46?V and yet the ring jumps more than 9?m high. The setup is suitable for both lectures and student laboratory work in higher education.

We present an experiment for education which demonstrates random transmission or reflection of heralded single photons on beam splitters. With our set-up, we can realize different quantum random experiments by appropriate settings of polarization rotators. The concept of entanglement is motivated by correlated randomness. The experiments are suitable for undergraduate education and are available as interactive screen experiments.

We report on an injection-seeded 9.5-W 82-MHz-repetition-rate picosecond optical parametric generator (OPG) based on a 55 mm long crystal of periodically poled lithium niobate (PPLN) with a quasi-phase-matching (QPM) grating period of 29.75 μm. The OPG is excited by a continuously diode pumped mode-locked picosecond Nd:YVO4 oscillator-amplifier system. The laser system generates 7 ps pulses with a repetition rate of 82.3 MHz and an average power of 24 W. Without injection-seeding the total average output power of the OPG is 8.9 W, which corresponds to an internal conversion efficiency of 50%. The wavelengths of the signal and idler waves were tuned in the range 1.57–1.64 μm and 3.03–3.3 μm, respectively, by changing the crystal temperature from 150 °C to 250 °C. Injection seeding of the OPG at 1.58 μm with 4 mW of single frequency continuous-wave radiation of a distributed-feedback (DFB) diode laser increases the OPG output to 9.5 W (53% conversion efficiency). The injection seeding increases the pulse duration and reduces the spectral bandwidth. When pumped by 10 W of 1.06 μm laser radiation, the duration of the signal pulses increased from 3.6 ps to 5.5 ps while the spectral bandwidth is reduced from 4.5 nm to 0.85 nm. Seeding thus improved the time-bandwidth product from 1.98 to a value of 0.56, much closer to the Fourier limit.

This paper reports on the pulse-to-pulse wavelength tuning of a multiwatt narrow-linewidth nanosecond optical parametric generator (OPG). The OPG consists of a 55 mm long periodically poled lithium niobate (PPLN) crystal with a domain period of 29.75 μm. Excited by 5.7 W of 1064 nm laser pulses (duration: 10 ns, repetition rate: 10 kHz, spatial beam quality M2=1.2) the OPG generates 1.78 W of signal radiation and 0.79 W of idler radiation. The total output of 2.57 W corresponds to a crystal internal efficiency of 64%. The wavelength and spectral width of the OPG is controlled by injecting the cw single mode radiation of a 1580.2 nm DFB diode laser. A seed power as low as 20 μW is sufficient for complete control of the wavelength and the (90 MHz) linewidth of the OPG output. Fast tuning of the diode laser frequency is possible with a rate of up to 6×107 GHz/s by changing the diode current. This allows pulse-to-pulse wavelength tuning of the 10 kHz OPG over a range of 25 GHz limited only by the maximum variation of the current (of 60 mA) allowed for the DFB diode laser used. Increasing the current from 35 mA to 95 mA changed the diode power from 0.3 mW to 5.7 mW. Since these power levels are well above the required minimum seed power, the change of the diode current changes the wavelength of the OPG, but not its linewidth or its output power.

We explore the potential of a new laser resonator design that uses an intracavity Fourier transformation and allows for multi-color operation, gain extension and intracavity second harmonic generation (SHG). First, purely electronically controlled wavelength tuning is demonstrated using liquid crystal displays (LCDs) and digital mirror devices. Moreover, the new design can be applied to different lasers as shown on the examples of a laser diode and a Thulium-doped fiber laser in the mid-infrared. Furthermore, we demonstrate the simultaneous control of multiple gain media within one single external cavity. In addition, tunable emission in the 490 nm range is obtained using intracavity SHG with one single control parameter. Finally, we unambiguously prove simultaneous multi-wavelength operation with variable wavelength spacings and apply it to the generation of THz difference frequencies.

The Barkhausen effect can be impaired by various noise sources. These are avoided by a hum-bucking coil, earthing, a preamplifier with carefully chosen bandwidth, and matching the input resistor to the inductance of the coil. The present setup is suitable for lecture hall demonstration in higher education institutes.

We describe a cw optical parametric oscillator (OPO) with multigrating periodically poled LiTaO(3) . Pumped by a single-frequency 532-nm laser, the OPO emits single-frequency radiation at wavelengths from 0.77 to 1.73 microm with as much as 60 mW of output power. Mode-hop-free operation for as long as 50 min, a low frequency drift (70 MHz/h), and as much as 700-MHz continuous frequency tuning of signal and idler are demonstrated.

We report on what is believed to be the first singly resonant cw optical parametric oscillator (SRO) that is directly pumped by a diode laser. The SRO consists of a 38-mm-long periodically poled LiNbO(3) crystal in a four-mirror signal-resonant ring cavity. Pumped by 2.5 W of 925-nm diode-laser radiation, the SRO generates 480 mW of single-frequency idler radiation at 2.1mum . The wavelengths of the signal and the idler output are tuned in the ranges of 1.55 to 1.70mum and 2.03 to 2.29mum, respectively, by tuning the wavelength of the diode laser from 924.0 to 925.4 nm.

We demonstrate the generation of sub-6-fs pulses centered at 405 nm by frequency doubling of 8.6-fs Ti:sapphire laser pulses. The frequency doubling is carried out in a nonlinearly chirped quasi-phase-matching grating fabricated in a lithium tantalate substrate. This device simultaneously provides frequency conversion and pulse compression of the positively prechirped fundamental pulses. The second-harmonic pulses are characterized in a cross-correlation setup, and their pulse shapes are retrieved by two iterative phase-reconstruction algorithms. The generated second-harmonic spectrum spans a bandwidth of 220 THz. To our knowledge, these are the shortest pulses ever generated in the blue spectral region.

A rotor of 12 cm diameter is attached to a precision electric motor, used as a generator, to make a model wind turbine. Output power of the generator is measured in a wind tunnel with up to 15 m s−1 air velocity. The maximum power is 3.4 W, the power conversion factor from kinetic to electric energy is cp = 0.15. The v3 power law is confirmed. The model illustrates several technically important features of industrial wind turbines quantitatively.

The properties of all-optical phase-coherent frequency division by 3, based on a self-phase-locked continuous-wave (cw) optical parametric oscillator (OPO), are investigated theoretically and experimentally. The frequency to be divided is provided by a diode laser master-oscillator power-amplifier system operated at a wavelength of 812 nm and used as the pump source of the OPO. Optical self-phase-locking of the OPO signal and idler waves is achieved by mutual injection locking of the signal wave and the intracavity frequency-doubled idler wave. The OPO process and the second-harmonic generation of the idler wave are simultaneously phase matched through quasi-phase-matching using two periodically poled sections of different period manufactured within the same LiNbO3 crystal. An optical self-phase-locking range of up to 1 MHz is experimentally observed. The phase coherence of frequency division by three is measured via the phase stability of an interference pattern formed by the input and output waves of the OPO. The fractional frequency instability of the divider is measured to be smaller than 7.6×10-14 for a measurement time of 10 s (resolution limited). The self-phase-locking characteristics of the cw OPO are theoretically investigated by analytically solving the coupled field equations in the steady-state regime. For the experimental parameters of the OPO, the calculations predict a locking range of 1.3 MHz and a fractional frequency instability of 1.6×10-15, in good agreement with the experimental results.

Summary form only given. We investigated the single pass second harmonic generation of a passively mode-locked Nd:YAlO/sub 3/ laser operating at /spl lambda/ = 930 nm in a bulk periodically poled LiTaO/sub 3/ (PPLT) crystal. The Nd:YAlO/sub 3/ laser was passively mode-locked with a semiconductor saturable absorber mirror (SESAM) in a V-shaped cavity.

Summary form only given. Singly-resonant continuous-wave (CW) optical parametric oscillators (SROs) have favourable properties in respect to power stability and wavelength tunability. A disadvantage is, however, the high pump power at threshold. The operation of singly resonant CW OPOs thus requires multiwatt laser radiation in a beam of good spectral and spatial quality. For this reason the CW SROs reported so far used high power solid-state lasers as pump sources. In the paper we present, to our knowledge, the first singly-resonant CW OPO which is directly pumped by a high power diode laser. The OPO is based on periodically poled lithium niobate (PPLN).

Applied Physics B, 74, ISSN:0946-2171, ISSN:1432-0649, ISSN:0721-7269, ISSN:0340-3793

We report on the first realization of a continuous-wave singly-resonant optical parametric oscillator (SRO) which is directly pumped by a diode laser.

We introduce a new concept for a wavelength-tunable frequency-doubled laser diode with a single control parameter. The concept is based on intracavity frequency doubling in an external resonator geometry with spatial separation of the spectral components. The use of a fan-structured periodically poled LiTaO(3) crystal permits tuning of both the fundamental and the second harmonic simultaneously with one aperture. We demonstrate tunability over more than 10 nm in the blue (480.4 to 490.6 nm) with output powers of the order of 50 nW.

We report an efficient, visible, nanosecond optical parametric generator of periodically poled lithium niobate pumped at 532 nm by a frequency-doubled, diode-pumped, passively Q -switched, single-mode Nd:YAG laser with 90-muJ pulse energy. The signal radiation is tunable from 637 to 593 nm. The maximum signal-conversion efficiency is 23%. Optical parametric amplification of a He-Ne laser at 632.8 nm is also studied.

We report on the fabrication and characterization of quasi-phase-matched potassium niobate crystals for second-harmonic generation. Periodic 30-mum -pitch antiparallel ferroelectric domains are fabricated by means of poling in an electrical field. Both birefrigence and periodic phase shift of the generated second harmonic contribute to phase matching when the d(31) nonlinear optical tensor element is used. 3.8 mW of second-harmonic radiation at 463 nm is generated by frequency doubling of the output of master-oscillator power-amplifier diode laser in a 5-mm-long crystal. The measured effective nonlinear coefficient is 3.7pm/V. The measured spectral acceptance bandwidth of 0.25 nm corresponds to the theoretical value.

We demonstrate a method that enables in situ modification of the spectral shape of the parametric-gain profile in quasi-phase-matching crystals. In our experiment we used the electro-optic effect to modify the phase-matching profile for second-harmonic generation in a 57-mm-long nonuniformly poled LiNbO3 crystal. In the direction of beam propagation the crystal is divided into three segments, where the first and the third segments have an equal length of 17 mm. Both segments are periodically poled with the same period of 21.6 µm, in order to obtain quasi phase matching for frequency doubling a fundamental wavelength of 1653 nm. The center segment is single-domain LiNbO3 whose index of refraction is changed by the electro-optic effect by applying a voltage. Using a continuously tunable, single-frequency, single-stripe, distributed-feedback diode laser as the fundamental source, we recorded the parametric phase-matching profile for second-harmonic generation as a function of the laser wavelength and investigated the modification of the profile in dependence of the voltage applied to the crystal center segment. The measured phase-matching spectra are in excellent agreement with the theoretical prediction. The demonstrated method opens the possibility of rapidly changing the parametric-gain profile for all types of χ(2) nonlinear conversion processes.