The development of optical methods in modern medicine in the areas of diagnostics, therapy, and surgery has stimulated the investigation of optical properties of various biological tissues, since the efficacy of laser treatment depends on the photon propagation and fluence rate distribution within irradiated tissues. In this work, an overview of published absorption and scattering properties of skin and subcutaneous tissues measured in wide wavelength range is presented. Basic principles of measurements of the tissue optical properties and techniques used for processing of the measured data are outlined.

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Optical properties of skin, subcutaneous, and muscle tissues: a review

Materials chemistry and the pursuit of new compounds through exploratory synthesis are having a strong impact in many technological fields. The field of nonlinear optics is directly impacted by the availability of enabling materials with high performance. Nonlinear optical (NLO) phenomena such as second harmonic and difference frequency generation (SHG and DFG, respectively) are effective at producing a coherent laser beam in difficult to reach frequency regions of the electromagnetic spectrum. Such regions include the infrared (IR), far-infrared, and terahertz frequencies. High performance NLO crystals are critical for applications utilizing these coherent light sources, and new materials are continuously sought for better conversion efficiency and performance. The class of metal chalcogenides is the most promising source of potential NLO materials with desirable properties particularly in the IR region where most classes of materials face various fundamental challenges. We review the recent developments...

Metal Chalcogenides: A Rich Source of Nonlinear Optical Materials

The primary goal of this review is to present a clear chemical perspective of borates in order to stimulate and facilitate the discovery of new borate-based optical materials. These materials, whic...

Borates: A Rich Source for Optical Materials.

2D Layered Materials: Synthesis, Nonlinear Optical Properties, and Device Applications

The family of metal thiophosphates is an important but long-ignored compound system of the nonlinear optical (NLO) materials with desirable properties for the mid-infrared (mid-IR) coherent light generation. In the present work, the mid-IR NLO capabilities of metal thiophosphate crystals are systematically investigated based on their structure-property relationship. The linear and nonlinear optical properties of these crystals are predicted and analyzed using the first-principles calculations. In particular, several metal thiophosphate compounds are highlighted to exhibit good mid-IR NLO performances, as supported by the primary experimental results. These candidates would greatly promote the development of the mid-IR NLO functional materials.

Metal Thiophosphates with Good Mid-infrared Nonlinear Optical Performances: A First-Principles Prediction and Analysis

The new nonlinear optical (NLO) crystal BaGa4S7 for the mid-infrared (IR) has been grown by a Bridgman-Stockbarger technique. Polycrystalline materials with stoichiometric composition were synthesized from BaS, Ga, and S as the initial materials by solid-state reactions. The ultraviolet (UV) and IR transmittance of the crystal was determined with polished crystal pieces. The UV and IR optical absorption edges were found to be at 350 nm and 13.7 μm, respectively. From optical measurements of second harmonic generation on powders, the NLO coefficient d33 was determined to be 12.6 pm/V. The laser damage threshold of a single crystal reached about 1.2 J/cm2 at 1.064 μm. The Vickers-hardness value of the crystal is 327.5 HV5, which is equivalent to Mohs’ hardness of about 5.

Growth and Characterization of BaGa4S7: A New Crystal for Mid-IR Nonlinear Optics

For polymer-supported metal thin films used in flexible electronics, the definition of the fatigue lifetime at microcrack nucleation (FLMN) should be more physically meaningful than all the previous definitions at structural instability. In this paper, the FLMN of Cu films (with thickness from 100 nm to 3.75 µm) as well as Al thin films (from 80 to 800 nm) was experimentally characterized at different strain ranges and different thicknesses by using a simple electrical resistance measurement (ERM). A significant thickness dependence was revealed for the FLMN and a similar Coffin–Manson fatigue relationship observed commonly in bulk materials was found to be still operative in both the films. Microstructural analyses were carried out to verify the feasibility of ERM correspondingly.

http://iopscience.iop.org/article/10.1088/0022-3727/41/19/195404/pdf

Thickness dependent fatigue life at microcrack nucleation for metal thin films on flexible substrates

A high power and efficient 588 nm yellow light is demonstrated through intracavity frequency doubling of an acousto-optic Q-switched self-frequency Raman laser. A 30-mm-length double-end diffusion-bonded Nd:YVO4 crystal was utilized for efficient self-Raman laser operation by reducing the thermal effects and increasing the interaction length for the stimulated Raman scattering. A 15-mm-length LBO with non-critical phase matching (θ = 90°, ϕ = 0°) cut was adopted for efficient second-harmonic generation. The focus position of incident pump light and both the repetition rate and the duty cycle of the Q-switch have been optimized. At a repetition rate of 110 kHz and a duty cycle of 5%, the average power of 588 nm light is up to 7.93 W while the incident pump power is 26.5 W, corresponding to an overall diode-yellow conversion efficiency of 30% and a slope efficiency of 43%.

Efficient second harmonic generation of double-end diffusion-bonded Nd:YVO4 self-Raman laser producing 7.9 W yellow light.

A high-power 588 nm light produced by an intracavity frequency-doubling acousto-optic Q-switched self-frequency Raman laser is reported. A 20-mm-long YVO4/Nd:YVO4 composite crystal and a 15-mm-long LiB3O5 (LBO) with noncritical phase-matching (θ=90°, ϕ=0°) cut were adopted for efficient self-Raman laser operation and second-harmonic generation, respectively. By the optimizing the focus position of incident pump light and Q-switch repetition rate, yellow light with 5.7 W average power was generated under the pump power of 23.5 W, corresponding to the overall diode-yellow conversion efficiency of 24.2% and slope efficiency of 32%. The pulse width is about 16 ns, and the pulse energy is up to 95 μJ.

Yellow-light generation of 5.7 W by intracavity doubling self-Raman laser of YVO 4 /Nd:YVO 4 composite

An ammonium-containing metal iodate fluoride compound, (NH4 )Bi2 (IO3 )2 F5 , featuring a two-dimensional double-layered framework constructed by [BiO2 F5 ]6- and [BiO4 F4 ]9- polyhedra, as well as [IO3 ]- groups, was successfully synthesized. The well-ordered alignment of these SHG-active units leads to an extraordinary strong SHG response of 9.2 times that of KDP. Moreover, this compound possesses a large birefringence (Δn=0.0690 at 589.3 nm), a wide energy band gap (Eg =3.88 eV), and a high laser damage threshold (LDT; 40.2×AgGaS2 ). In particular, thermochromic behavior was observed for the first time in this type of compound. Such multifunctional crystals will expand the application of nonlinear optical materials.

(NH 4 )Bi 2 (IO 3 ) 2 F 5 : An Unusual Ammonium‑Containing Metal Iodate Fluoride Showing Strong Second Harmonic Generation Response and Thermochromic Behavior

Ge Zhang

Papers

Growth and Characterization of BaGa4S7: A New Crystal for Mid-IR Nonlinear Optics

Thickness dependent fatigue life at microcrack nucleation for metal thin films on flexible substrates

Efficient second harmonic generation of double-end diffusion-bonded Nd:YVO4 self-Raman laser producing 7.9 W yellow light.

Yellow-light generation of 5.7 W by intracavity doubling self-Raman laser of YVO 4 /Nd:YVO 4 composite

(NH 4 )Bi 2 (IO 3 ) 2 F 5 : An Unusual Ammonium‑Containing Metal Iodate Fluoride Showing Strong Second Harmonic Generation Response and Thermochromic Behavior