Abstract A simple short-pulse generator circuit based on electronic gates is designed for short electric pulse of about 12 ns at Full Width at Half Maximum (FWHM) and 3.6 Volt amplitude for driving a laser diode. Using our circuit with a 780 nm laser diode designed and fabricated for producing short light pulses. The circuit utilizes an AND gate, a XOR gate, and a common function generator, provides a repetition rate from DC up to 1 MHz. The laser pulses were generated and then detected via an avalanche photodiodes (APD). This finding can benefit the field of light-based quantum information including single photon experiments.
Abstract A simple short-pulse generator circuit based on electronic gates is designed for short electric pulse of about 12 ns at Full Width at Half Maximum (FWHM) and 3.6 Volt amplitude for driving a laser diode. Using our circuit with a 780 nm laser diode designed and fabricated for producing short light pulses. The circuit utilizes an AND gate, a XOR gate, and a common function generator, provides a repetition rate from DC up to 1 MHz. The laser pulses were generated and then detected via an avalanche photodiodes (APD). This finding can benefit the field of light-based quantum information including single photon experiments.
A series of simple and low-cost devices for switching, amplifying, and chirping diode lasers based on current modulation are presented. Direct modulation of diode laser currents is rarely sufficient to establish precise amplitude and phase control over light, as its effects on these parameters are not independent. These devices overcome this limitation by exploiting amplifier saturation and dramatically outperform commonly used external modulators in key figures of merit for quantum technological applications. Semiconductor optical amplifiers operated on either rubidium D line are recast as intensity switches and shown to achieve ON:OFF ratios >106 in as little as 50 ns. Current is switched to a 795 nm wavelength (Rb D1) tapered amplifier to produce optical pulses of few nanosecond duration and peak powers of 3 W at a similar extinction ratio. Fast rf pulses are applied directly to a laser diode to shift its emission frequency by up to 300 MHz in either direction and at a maximum chirp rate of 150 MHz ns-1. Finally, the latter components are combined, yielding a system that produces watt-level optical pulses with arbitrary frequency chirps in the given range and <2% residual intensity variation, all within 65 ns upon asynchronous demand. Such systems have broad application in atomic, molecular, and optical physics and are of particular interest to fast experiments simultaneously requiring high power and low noise, for example, quantum memory experiments with atomic vapors.
Among various implementations of single-photon sources, faint-pulse single-photon sources provide a simple and practical approach based on attenuated coherent laser pulses. This work presents an experimental realization of a faint-pulse single-photon source using a 785-nm Grating Stabilized Laser Diode system, driven by a laser diode controller and modulated by a Field Programmable Gate Array (FPGA). The system's performance was evaluated by analyzing the photon detection rate as a function of pulse width and driving current. Results indicated a linear relationship between the single-photon detection rate and pulse width and an exponential dependence on driving current. The system achieved a photon emission probability of 10% per pulse, aligning with the requirements of practical quantum key distribution systems. This implementation demonstrates a cost-effective, scalable, and accessible platform for single-photon experiments, providing a foundation for future implementations of quantum communication protocols.
The advent of quantum computers marks the beginning of the quantum 2.0 era. Unlike classical computers, quantum computers have faster and more efficient computational abilities, enabling them to break classical encryption such as the RSA (Rivest-Shamir-Adlemar) algorithm in a matter of minutes. To address this threat, a quantum communication system is required, which possesses quantum properties as well. The urgency of developing an independent and autonomous quantum communication system is crucial for a country. In this research, a transmitter for quantum communication based on faint pulse laser is developed. A weakened laser diode is used as the photon source. The laser diode weakening is achieved using a laser driver that generates short-duration pulse signals. By combining AND and XOR logic gates in such a way that when given a square wave input, the output of the logic gate system can produce short-duration pulses. The information in this communication system consists of randomly implemented keys, realized using the myRIO board and serving as a subsystem for random port selection. The designed laser driver produces pulse signals with a width of 128 nanoseconds and an amplitude of 1.5168 V. Additionally, the random port selection subsystem has been successfully designed using the myRIO board. Random numbers from ‘0’ to ‘3’ are generated uniformly. From 100 observation samples, an expected value of 1.445 and a variance of 0.911 are obtained. In the subsequent research, observations of single photon and the generated keys will be conducted.
Entangled photon sources have applications in such fields as quantum communications, quantum sensing and quantum computing. Of particular interest are pulsed entangled photon sources, as they provide an additional degree of freedom – the temporal degree of freedom – to manipulate entanglement properties, hence increasing the information capacity of the entangled photons they produce. An entangled photon source in the telecom wavelength typically requires a 780 nm pump laser. So far, in most cases, pulsed entangled photon sources are pumped by the Ti:Sapph mode-locked laser, which, due to its bulky size and high cost, has limited the widescale adoption of pulsed entangled photon sources. In this thesis, I demonstrate a simple, cost-effective, pulsed laser diode capable of competing with the Ti:Sapph for the purposes of entangled photon generation. The diode and driver are capable of pulsing at up to 60 MHz , with peak power exceeding 1 W and pulse energy in excess of 1 nJ , and with a spectral width narrower than 0.1 nm. I also demonstrate a pulsed, fully fiber-based, entangled photon source, with high entanglement quality (maximum concurrence of 0.985) and a high pair generation rate (0.15 pairs/pulse). The source is to our knowledge the first of its kind.
Experimental demonstration of a quantum random number generator based on one single-photon avalanche diode (SPAD) detector, a T / ( T − t ) pulse-shaped laser, and an field-programmable gate array (FPGA) acquisition module is presented. An integrated laser driver drives an external laser diode at 670 nm wavelength, whereas the SPAD with a photon detection probability of 18.5% is integrated together with an active quenching-resetting circuit. The SPAD detector generates counts for the interarrival time (IAT) measurement system implemented in an FPGA, where the change of the IATs between consecutive pulses is used to derive a random bit stream. It is shown how the application of a pulse-shaped laser driver can increase the performance of the system as compared to the continuous-wave operation of the laser diode to achieve the maximum generation rate of 5 Mbps while using a single SPAD. The generated numbers pass all randomness tests of the National Institute of Standards and Technology (NIST), Dieharder, and ENT test (pseudorandom number sequence test) suits.
A single-photon detection system with laser of 1310nm wavelength as light source is designed. Using InGaAs Avalanche Photodiode (InGaAs-APD) as single-photon detection device for quantum cryptography communication, the bias-voltage formation, low-temperature control and single-photon signal detection are comprehensively considered. The photon gate formed by pulse superimposed on DC level is equivalently performed by monostable circuit in pulse generator. Detection sensitivity of the system is improved by using a trans-impedance pre-amplifier and a precision comparator. The detection experiments in initial stage show that the waveform of -93dBm light signal can be observed by the detection system.