Previously we focused on fundamental transverse mode selection (TMS#0) of broad area semiconductor lasers (BALs) with two-arm folded integrated resonators for Fourier-optical spatial frequency filtering. The resonator had a round-trip length of 4f, where f is the focal length of the Fourier-transform element (FTE), that is, a cylindrical mirror in-between the orthogonal resonator branches. This 4f set-up can be called “retracted once” due to the reflective filter after 2f; that is, the 2f path was used forwards and backwards. Now the branches are retracted once more resulting in a compact 1f long linear resonator (called “retracted twice”) with a round-trip length of 2f. One facet accommodates the filter, while the other houses the FTE, now incorporating a film-waveguide lens. The BAL facet with the filter represents both the Fourier-transform plane (after 2f, i.e., one round-trip) as well as the image plane (after 4f, two round-trips). Thus filtering is performed even after 4f, not just after 2f. Experimental results reveal good fundamental TMS for pump currents up to 20% above threshold and a one-dimensional beam quality parameter <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.834pt" id="M1" height="15.4254pt" version="1.1" viewBox="-0.0498162 -11.5914 24.1077 15.4254" width="24.1077pt"><g transform="matrix(.013,0,0,-0.013,0,0)"><path id="g113-78" d="M962 650H795L470 145L347 650H176L170 622C268 613 275 606 244 503L190 322C150 188 132 126 118 91C102 50 80 33 18 28L12 0H245L251 28C175 35 170 48 174 93C177 128 191 180 220 284L292 542H294C331 392 383 150 409 4H432L774 555H776L714 137C700 40 694 34 612 28L606 0H868L874 28C793 34 784 37 797 137L849 533C859 612 863 616 956 622L962 650Z"/></g><g transform="matrix(.0091,0,0,-0.0091,12.807,-5.741)"><path id="g50-51" d="M414 144C384 79 371 75 317 75H135L276 221C367 316 408 376 408 465C408 570 327 635 237 635C179 635 131 609 100 575L42 494L67 471C94 510 138 565 205 565C277 565 321 517 321 435C321 348 258 270 195 195C146 137 88 81 33 26V0H411C423 44 433 88 446 135L414 144Z"/></g><g transform="matrix(.0091,0,0,-0.0091,12.22,3.784)"><path id="g50-50" d="M389 0V32C297 38 291 46 291 118V635C234 613 175 595 109 583V556L161 554C203 552 207 547 207 497V118C207 46 201 38 110 32V0H389Z"/></g><g transform="matrix(.0091,0,0,-0.0091,16.652,3.784)"><path id="g58-66" d="M43 650V617C122 612 130 606 130 522V128C130 44 122 37 34 32V0H275C400 0 497 25 573 82C652 142 698 229 698 350C698 445 662 518 613 565C549 625 456 650 327 650H43ZM217 544C217 580 220 591 229 599C240 607 264 613 311 613C380 613 437 599 482 570C561 523 598 436 598 336C598 177 511 40 324 40C248 40 217 61 217 135V544Z"/></g></svg> = 1.47. The BALs are made from AlGaInAsSb, but the concept can equally well be employed for BALs of any material system.

Henning Fouckhardt

Ann-Kathrin Kleinschmidt

Johannes Strassner

Christoph Doering

Fundamental Transverse Mode Selection (TMS#0) of Broad Area Semiconductor Lasers with Integrated Twice-Retracted 4f Set-Up and Film-Waveguide Lens

In order to solve the problem that the measure precision of coal roof rock strain amount detection using traditional electric sensor is insufficient, a kind of High Sensitive Surface-Pasted Fiber Bragg Grating Strain Sensor based on rock bolting is designed for substitution. Furthermore, a kind of Reference Grating Zero-Strain method based on sensitivity matrix coefficient is proposed for solving FBG strain-temperature cross-sensitivity problem and realizing the better separation relevant to strain and temperature. It is proved that the sensitivity and measurement precision and anti-interference ability of FBG strain sensors are better than traditional electricity class sensors, being able to realize the real-time and online detection for coal roof surrounding rock strain.

Zhang Jian

Lu Chuan

Lin De-Shu

Method Research of Coal Mine Roof Strain Detection Based on the Fiber Bragg Grating Sensor with Thermodynamic Couple Numerical Condition

A cascaded intensity modulator (IM) and phase modulator (PM) are used to modulate a continuous-wave (CW) laser and generate an optical frequency comb (OFC). Thus, the generated comb is utilized as an initial seed and combined with another CW-laser to generate four-wave mixing (FWM) in photonic crystal fiber (PCF). Results show that an initial flat 30&#x2009;GHz OFC of 29, 55 lines within power fluctuation of 0.8&#x2009;dB and 2&#x2009;dB, respectively, can be achieved by setting the ratio of the DC bias to amplitude of sinusoidal signal at 0.1 and setting the modulation indices of both IM and PM at 10. Moreover, the 1st order of FWM created through 14&#x2009;m of PCF has over 68 and 94 lines with fluctuation of 0.8&#x2009;dB and 2&#x2009;dB, respectively. Hence, the generated wavelengths of 1st left and right order of FWM can be tuned in a range from &#x7e;1500&#x2009;nm to &#x7e;1525&#x2009;nm and &#x7e;1590&#x2009;nm to &#x7e;1604&#x2009;nm, respectively.

Tawfig Eltaif

Broadband Enhancement of Optical Frequency Comb Using Cascaded Four-Wave Mixing in Photonic Crystal Fiber

Intensive studies have been done to get robust encryption algorithms. Due to the importance of image information, optical encryption has played a vital role in information security. Many optical encryption schemes have been proposed but most of them suffer from poor robustness. In this paper six proposed algorithms will be presented for optical encryption to be robust to severe attacks: composite attack. Three of these approaches are based on one level Discrete Wavelet Transform (DWT) and the others are based on Wavelet Packet (WP). Not only will new techniques be presented but also a new proposed chaotic map has been developed as random keys for all algorithms. After extensive comparative study with some traditional techniques, it has been found that the novel algorithms have achieved better performance versus conventional ones. Also it has been found that WP based algorithms have achieved better performance than DWT based ones against severe composite attacks.

M. A. Mohamed

Ahmed Shaaban Samrah

Mohamed Ismail Fath Allah

DWT versus WP Based Optical Color Image Encryption Robust to Composite Attacks

The evolution of a fiber-fuse phenomenon in a single-mode optical fiber was studied theoretically. To clarify both the silica-glass densification and cavity formation, which have been observed in fiber fuse propagation, we investigated a nonlinear oscillation model using the Van Der Pol equation. This model was able to phenomenologically explain both the densification of the core material and the formation of periodic cavities in the core layer as a result of a relaxation oscillation.

Yoshito Shuto

Cavity Formation Modeling of Fiber Fuse in Single-Mode Optical Fibers

A theoretical study of electromagnetic wave propagation in parallel plate chirowaveguide is presented. The waveguide is filled with a chiral material having diagonal anisotropic constitutive parameters. The propagation characterization in this medium is based on algebraic formulation of Maxwell&#x2019;s equations combined with the constitutive relations. Three propagation regions are identified: the fast-fast-wave region, the fast-slow-wave region, and the slow-slow-wave region. This paper focuses completely on the propagation in the first region, where the dispersion modal equations are obtained and solved. The cut-off frequencies calculation leads to three cases of the plane wave propagation in anisotropic chiral medium. The particularity of these results is the possibility of controlling the appropriate cut-off frequencies by choosing the adequate physical parameters values. The specificity of this study lies in the bifurcation modes confirmation and the possible contribution to the design of optical devices such as high-pass filters, as well as positive and negative propagation constants. This negative constant is an important feature of metamaterials which shows the phenomena of backward waves. Original results of the biaxial anisotropic chiral metamaterial are obtained and discussed.

S. Aib

F. Benabdelaziz

C. Zebiri

D. Sayad

Propagation in Diagonal Anisotropic Chirowaveguides

Avalanche photodiodes (APDs) are key optical receivers due to their performance advantages of high speed, high sensitivity, and low noise. The most critical device parameters of APD include the avalanche breakdown voltage and dark current. In this work, we study the temperature dependence of the breakdown voltage and dark current of the mesa-type APD over a wide temperature range of 20&#x2013;145&#xb0;C. We institute an empirical model based on impact ionization processes to account for the experimental data. It is shown that highly stable breakdown characteristics of mesa-type APD can be attained with the optimization of the multiplication layer design. We have achieved excellent stability of avalanche breakdown voltage with a temperature coefficient of 0.017&#x2009;V/&#xb0;C. The temperature dependence of dark current is attributed to generation-recombination mechanism. The bandgap energy is estimated to be about 0.71&#x2009;eV based on the temperature variation of dark current, in good agreement with the value for InGaAs.

Jack Jia-Sheng Huang

H. S. Chang

Yu-Heng Jan

C. J. Ni

H. S. Chen

Emin Chou

Temperature Dependence Study of Mesa-Type InGaAs/InAlAs Avalanche Photodiode Characteristics

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Advances in OptoElectronics ceased publication in 2019 and is no longer accepting submissions.

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Advances in OptoElectronics publishes papers on the theory, design, fabrication, and applications of devices and components that convert light into an electrical current or, conversely, an electric current into light.

Advances in OptoElectronics