Coherent tunable diffractional pulse shaping and generation of the 0π-pulse in Rb vapor

We have experimentally studied for the first time a new operation principle of the coherent diffractional pulse shaper (Rabi shaper). In the experiment, we observed an effect of tunable pulse shaping of nanosecond semiconductor laser pulse during the resonant pumping of the D2 line (780.24 nm) of 87Rb vapor in the range of self-diffraction angles φ = ± 4°. We observed the synthesis of nanosecond 0π-pulses at the small length of the nonlinear interaction 0.1…1 mm. We propose to use the Rabi shaper as an energy efficient tunable shaper of classical and single-photon wave packets. We analyze a possibility of the Rabi shaper operation in quantum systems with feedback.

Synchronized multi-wavelength soliton fiber laser via intracavity group delay modulation

Locking of longitudinal modes in laser cavities is the common path to generate ultrashort pulses. In traditional multi-wavelength mode-locked lasers, the group velocities rely on lasing wavelengths due to the chromatic dispersion, yielding multiple trains of independently evolved pulses. Here, we show that mode-locked solitons at different wavelengths can be synchronized inside the cavity by engineering the intracavity group delay with a programmable pulse shaper. Frequency-resolved measurements fully retrieve the fine temporal structure of pulses, validating the direct generation of synchronized ultrafast lasers from two to five wavelengths with sub-pulse repetition-rate up to ~1.26 THz. Simulation results well reproduce and interpret the key experimental phenomena, and indicate that the saturable absorption effect automatically synchronize multi-wavelength solitons in despite of the small residual group delay difference. These results demonstrate an effective approach to create synchronized complex-structure solitons, and offer an effective platform to study the evolution dynamics of nonlinear wavepackets.

Computer simulation of a power source based on a bipolar pulse shaper for magnetron sputtering systems

The research object is a pulsed bipolar power supply based on a bipolar pulse shaper of increased frequency for magnetron sputtering systems. The research subject is the electrophysical and electromagnetic processes occurring in the bipolar pulse shaper when it is operated with a magnetron sputtering system, as well as the control characteristics. The purpose of the paper is the possibility of creating a pulsed power supply with a power of up to several tens of kW, which makes it possible to increase the stability of the magnetron sputtering system. Besides, the outcomes of computer simulation of a power source based on a bipolar pulse shaper and control algorithm ensuring its stable and reliable operation in association with a magnetron sputtering system are reflected in the paper. The results show that the deviation of the output control characteristics of the bipolar pulse shaper from the analytically obtained characteristics does not exceed 3%. Circuit modeling is carried out in the Swicher CAD/LTspice software package. The mathematical SPICE models of the field-effect STY112N65M5 transistor, transistor IGBT of IRF4PF50WD and STTH8006 diode are taken from the websites of STMicroelectronics and International Rectifier manufacturers.

Full quantum state tomography of high-dimensional on-chip biphoton frequency combs with randomized measurements

Owing in large part to the advent of integrated biphoton frequency combs (BFCs), recent years have witnessed increased attention to quantum information processing in the frequency domain for its inherent high dimensionality and entanglement compatible with fiber-optic networks. Quantum state tomography (QST) of such states, however, has required complex and precise engineering of active frequency mixing operations, which are difficult to scale. To address these limitations, we propose a novel solution that employs a pulse shaper and electro-optic phase modulator (EOM) to perform random operations instead of mixing in a prescribed manner. Incorporating state-of-the-art Bayesian statistical method, we successfully verify the entanglement and reconstruct the full density matrix of BFCs generated from an on-chip Si3N4 microring resonator (MRR) in up to an 8×8-dimensional two-qudit Hilbert space, the highest dimension to date for frequency bins. Overall, our method furnishes an experimentally powerful approach for frequency-bin tomography with readily implementable operations.

Acousto-optic Light Pulse Shaper for Measuring the Parameters of Photo-detectors

The paper emphasizes that intensive utilization of the optical range increases the need for the development of new optoelectronic devices. Accordingly, there is a growth in the need for effective methods and tools to study photoelectric properties of semiconductor materials, including photo-detectors.In the paper we have analyzed the well-known methods and tools for measuring the photo-detector parameters, defined the restrictions in their applications, and proved that it is relevant to create a measuring system, the parameters of which are easily adapted to the study of photoelectric characteristics of a wide range of semiconductor materials, including photo-detectors.The scheme and principle of operation of the acousto-optic processor and the features of the photo-elastic effect are discussed, and it is proved that they can be used to form a light pulse of required duration and power. The expressions obtained for calculating the response at the acousto-optic processor output enable us to estimate separately the effects of time of crossing the optical beam by the elastic wave packet and the photo-detector inertia.The capability to determine the time of crossing the optical beam by the elastic wave packet and taking it into account as a device error has been substantiated. The proposed formulas have been tested and by numerical analysis based on the datasheet specifications of the FD-24K photodiode, the effectiveness of the obtained expressions has been convincingly proven.The inertia parameters of a particular sample of the FD-24K photodiode are experimentally studied. The emphasis is upon measuring the rise time of the transient response of the object under study. The exact rise time value of the transient response of the experimental FD-24K sample was approximately 7 μs, which is less than that indicated (≤10 μs) in the product certificate. In real life, such a measurement is necessary when selecting the photodiode pairs with identical parameters.By comparing the results of numerical analysis and experimental studies, it has been convincingly proven that the features of the photo-elastic effect can be used to construct a light pulse shaper with the required parameters.

Terahertz Waveguide-Based Pulse-Shaper System Analysis and Modeling

In this paper, the transfer function of a passive waveguide-based terahertz pulse shaper is achieved using the time domain data provided by the full-wave simulation of the structure. The fractional order of the transfer function is determined based on the time response resulting from an arbitrary excitation of the proposed pulse shaper. The full-wave electromagnetic numerical analyses are applied to attain the time-domain output data of the helical gold-ribbon dielectric-lined waveguide as the terahertz pulse shaper. In order to verify the simulation results, the proposed device has been examined using two different numerical methods which are the Finite Element Method (FEM) and the Finite Integral Technique (FIT). A good agreement was found between the results of FIT and FEM methods. The use of the system transfer function to analyze the structure is preferable to the full-wave simulation because of saving the execution time. Once the transfer function is determined, one could apply it for the subsequent time-domain analysis of the pulse shaper with various inputs.

Ohmic contacts to n-type and p-type gallium antimonide whiskers

The ohmic contacts to the n-type conductivity gallium antimonide whiskers were created due to a current pulse shaper. It was established that I–V characteristics of GaSb whiskers at low temperatures are linear, regardless of the direction of current transmission. That allows using the investigated techniques to create electrical contacts and study their electrophysical characteristics. GaSb samples with a diameter of 12 μm and 20 μm were studied at temperatures 4.2 K and 77 K. A slide table with bath and microfurnace was made for welding ohmic contacts to GaSb whiskers. Gold microwire with a diameter of 30 μm was used as a contact material. The melting was carried out under the flux layer. It was revealed that the fusion is one of the most suitable methods for creating contacts to the whiskers grown by gas transport reactions.