The objective of this paper is to give a comprehensive introduction to applied cryptography with an engineer or computer scientist in mind. The emphasis is on the knowledge needed to create practical systems which supports integrity, confidentiality, or authenticity. Topics covered includes an introduction to the concepts in cryptography, attacks against cryptographic systems, key use and handling, random bit generation, encryption modes, and message authentication codes. Recommendations on algorithms and further reading is given in the end of the paper. This paper should make the reader able to build, understand and evaluate system descriptions and designs based on the cryptographic components described in the paper.

[서평]「Applied Cryptography」

Organic–inorganic hybrid perovskite materials are attracting great interest for their applications in photovoltaics where they have demonstrated excellent efficiency. Here, Dou et al. demonstrate room temperature, solution-processed hybrid perovskite photodetectors with fast response and high detectivity.

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Solution-processed hybrid perovskite photodetectors with high detectivity

This review highlights the recent progress which has been made towards improved single-photon detector technologies and the impact these developments will have on quantum optics and quantum information science.

Single-photon detectors for optical quantum information applications

Chaos is good, if you are looking to send encrypted information across a broadband optical network. The idea that the transmission of light-based signals embedded in chaos can provide privacy in data transmission has been demonstrated over short distances in the laboratory. Now it has been shown to work for real, across a commercial fibre-optic channel in the metropolitan area network of Athens, Greece. The results show that the technology is robust to perturbations and channel disturbances unavoidable under real-world conditions. Chaotic signals have been proposed as broadband information carriers with the potential of providing a high level of robustness and privacy in data transmission1,2. Laboratory demonstrations of chaos-based optical communications have already shown the potential of this technology3,4,5, but a field experiment using commercial optical networks has not been undertaken so far. Here we demonstrate high-speed long-distance communication based on chaos synchronization over a commercial fibre-optic channel. An optical carrier wave generated by a chaotic laser is used to encode a message for transmission over 120 km of optical fibre in the metropolitan area network of Athens, Greece. The message is decoded using an appropriate second laser which, by synchronizing with the chaotic carrier, allows for the separation of the carrier and the message. Transmission rates in the gigabit per second range are achieved, with corresponding bit-error rates below 10-7. The system uses matched pairs of semiconductor lasers as chaotic emitters and receivers, and off-the-shelf fibre-optic telecommunication components. Our results show that information can be transmitted at high bit rates using deterministic chaos in a manner that is robust to perturbations and channel disturbances unavoidable under real-world conditions.

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Chaos-based communications at high bit rates using commercial fibre-optic links

Squeezed states of the electromagnetic field have been generated by nondegenerate four-wave mixing due to Na atoms in an optical cavity. The optical noise in the cavity, comprised of primarily vacuum fluctuations and a small component of spontaneous emission from the pumped Na atoms, is amplified in one quadrature of the optical field and deamplified in the other quadrature. These quadrature components are measured with a balanced homodyne detector. The total noise level in the deamplified quadrature drops below the vacuum noise level.

Observation of squeezed states generated by four-wave mixing in an optical cavity

The laser diode self-mixing (or feedback) interferometric technique is reviewed as a general tool for remote sensing applications. The operating principle is outlined, and the attainable performance is compared to conventional coherent detection. Applications to metrology and to new sensing schemes are described, experimental results are reported and the overall performance of the sensors are assessed.

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Laser diode self-mixing technique for sensing applications

We report what, to our knowledge, is the first example of laser feedback interferometer capable of measuring displacements of arbitrary form using a single interferometric channel. With a GaAlAs laser diode we can measure 1.2-m displacements, with interferometric resolution, simply by means of the backreflection from the surface (reflective or diffusive) under test. The operation is performed at moderate (i.e., not very weak) levels of feedback, such that a two-level hysteresis is found in the amplitude modulated signal. This is shown to allow the recovery of displacement without sign ambiguity from a single interferometric signal. Experimental results are reported, which are found to be in good agreement with the underlying theory. Performances of the developed feedback interferometer are finally presented. >

Laser diode feedback interferometer for measurement of displacements without ambiguity

In this review, self-mixing interferometry (SMI), a new configuration of interferometry, is discussed. SMI has practical advantages compared to standard interferometry, for example SMI does not require any optical part external to the laser chip and can be employed in a variety of measurements. Applications range from the traditional measurements related to optical pathlength – like displacement, small-amplitude vibrations, velocity – to sensing of weak optical echoes – for return loss and isolation factor measurements, CD readout and scroll sensing – and also, a special feature because of the interaction with the medium, measurements of physical parameters, like the laser linewidth, coherence length, and the alfa factor. Because it is also a coherent detection scheme, the SMI works close to the quantum limit of the received field, typically -90 dBm, so that minimum detectable amplitudes of 100 pm/ √Hz are currently achieved upon operation on diffusive targets, whereas a corner cube allows half-wavelength counting mode – or 0.5 μm resolution – on a dynamic range up to 2 m and more. With its compact setup, the SMI is easy to deploy in the field and can interface a variety of experiments – from MEMS testing to rotating machines vibration testing to pickup of biological motility. The illustration shows a double-channel, differential SMI incorporated in a thermomechanical test equipment to trace the mechanical hysteresis cycle of the beads of a motor-engine brake.

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Developing self‐mixing interferometry for instrumentation and measurements

A new method for the measurement of the linewidth enhancement factor of semiconductor lasers is presented, based on the interferometric self-mixing effect. It is a fast and easy to perform method that does not require radio frequency nor optical spectrum measurements. A small fraction of the emitted light is backreflected into the laser cavity by a remote target driven by a sine waveform. The mixing of the returned and the lasing fields generates a modulation of the optical output power in the form of an interferometric waveform, with a shape that depends on the optical feedback strength and the linewidth enhancement factor /spl alpha/, according to the well-known Lang-Kobayashi theory. We show that the value of /spl alpha/ can be retrieved from a simple measurement of two characteristic time intervals of the interferometric waveform. Experimental results obtained on different laser diodes show an accuracy of /spl plusmn/6.5%.

Measurement of the linewidth enhancement factor of semiconductor lasers based on the optical feedback self-mixing effect

Theory and experiments of single-mode ridge waveguide GaAs-AlGaAs semiconductor ring lasers are presented. The lasers are found to operate bidirectionally up to twice the threshold, where unidirectional operation starts. Bidirectional operation reveals that just above threshold, the lasers operate in a regime where the two counterpropagating modes are continuous wave. As the injected current is increased, a new regime appears where the intensities of the two counterpropagating modes undergo alternate sinusoidal oscillations with frequency in the tens of megahertz range. The regime with alternate oscillations was previously observed in ring lasers of the gas and dye type, and it is here reported and investigated in semiconductor ring lasers. A theoretical model based on a mean field approach for the two counterpropagating modes is proposed to study the semiconductor ring laser dynamics. Numerical results are in agreement with the regime sequence experimentally observed when the injected current is increased (i.e., bidirectional continuous-wave, bidirectional with alternate oscillations, unidirectional). The boundaries of the different regimes are studied as a function of the relevant parameters, which turn out to be the pump current and the conservative and dissipative scattering coefficients, responsible for an explicit linear coupling between the two counterpropagating field modes. By a fitting procedure, we obtain good numerical agreement between experiment and theory, and also an estimation for the otherwise unknown scattering parameters.

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Silvano Donati

Papers

Laser diode self-mixing technique for sensing applications

Laser diode feedback interferometer for measurement of displacements without ambiguity

Developing self‐mixing interferometry for instrumentation and measurements

Measurement of the linewidth enhancement factor of semiconductor lasers based on the optical feedback self-mixing effect

Operating regimes of GaAs-AlGaAs semiconductor ring lasers: experiment and model