250-MHz synchronously pumped optical parametric oscillator at 2.25-2.6 {\mu}m and 4.1-4.9 {\mu}m

A compact and versatile femtosecond mid-IR source is presented, based on an optical parametric oscillator (OPO) synchronously pumped by a commercial 250-MHz Er:fiber laser. The mid-IR spectrum can be tuned in the range 2.25-2.6 \mu m (signal) and 4.1-4.9 \mu m (idler), with average power from 20 to 60 mW. At 2.5 \mu m a minimum pulse duration of 110 fs and a power of 40 mW have been obtained. Active stabilization of the OPO cavity length has been achieved in the whole tuning range

PEMBERDAYAAN PEREMPUAN BERBASIS KREATIFITAS DI DUSUN MOJOREJO DESA JUNREJO KOTA BATU

Keadaan perekonomian saat ini sangat memprihatinkan khususnya di Indonesia yang terdapat berbagai permasalahan yang menyangkut mengenai kehidupan bermasyarakat, antara lain masalah kemiskinan, masalah pengangguran, masalah lingkungan hidup, dan lain-lain. Permasalahan tersebut timbul akibat semakin meningkatnya keadaan ekonomi yang tidak disesuaikan dengan kondisi masyarakat. Khususnya masyarakat menengah kebawah. Kemiskinan menjadi masalah yang penting saat ini di Indonesia, sehingga menjadi suatu fokus perhatian bagi pemerintah Indonesia. Masalah kemiskinan ini sangatlah kompleks karena berkaitan dengan aspek sosial, ekonomi, budaya, dan aspek lainnya. Kemiskinan terus menjadi masalah fenomenal di belahan dunia, khususnya Indonesia yang merupakan negara berkembang. Kemiskinan telah membuat jutaan anak tidak bisa mengenyam pendidikan, kesulitan membiayai kesehatan, kurangnya tabungan dan investasi, dan masalah lain yang menjurus ke arah tindakan kekerasan dan kejahatan. Kemisikinan menjadi salah satu fenomena masalah yang kerap kita temui di majalah, surat kabar, ataupun berita online lainnya. Dinas sosial Kota Batu setidaknya mencatat ada 2.339 keluarga miskin sedangkan badan pusat statistik menerangkan jumlah keluarga miskin mencapai 2.600 keluarga miskin. Ini cukup membuktikan untuk menjelaskan bahwa masih banyak keluarga Kota Batu yang masih harus berjuang hanya untuk sekedar membiayai anaknya masuk sekolah. Pemberdayaan menjadi salah satu alternatif untuk menyelesaikan masalah terkait dengan pengentasan kemiskinan. Dalam penelitian ini terkait dengan program pemberdayaan yang dilakukan oleh kelompok mahasiswa Universitas Muhammadiyah Malang dan didanai oleh DIKTI dari Program Kreatifitas Mahasiswa (PKM) yang mana saya termasuk dalam kelompok tersebut. Pengabdian masyarakat dalam bentuk pemberdayaan masyarakat ini mempunyai subyek pemberdayaan perempuan dusun Wonorejo Desa Junrejo Kota Batu. Proses pemberdayaan dilakukan selama tiga bulan di dusun setempat

The effect of gain saturation in a gain compensated perfect lens

The transmission of evanescent waves in a gain-compensated perfect lens is discussed. In particular, the impact of gain saturation is included in the analysis, and a method for calculating the fields of such nonlinear systems is developed. Gain compensation clearly improves the resolution; however, a number of nonideal effects arise as a result of gain saturation. The resolution associated with the lens is strongly dependent on the saturation constant of the active medium.Comment: to appear in J. Opt. Soc. Am.

Inverse scattering of dispersive stratified structures

We consider the inverse scattering problem of retrieving the structural parameters of a stratified medium consisting of dispersive materials, given knowledge of the complex reflection coefficient in a finite frequency range. It is shown that the inverse scattering problem does not have a unique solution in general. When the dispersion is sufficiently small, such that the time-domain Fresnel reflections have durations less than the round-trip time in the layers, the solution is unique and can be found by layer peeling. Numerical examples with dispersive and lossy media are given, demonstrating the usefulness of the method for e.g. THz technology

Optical fibers with periodic structures

This thesis concerns some experimental and theoretical issues in fiber optics. In particular, properties and devices based on photonic crystal fibers (PCFs) are investigated. The work can be grouped into three parts. In the first part we use sound to control light in PCFs. The lowest order flexural acoustic mode of various PCFs is excited using an acoustic horn. The acoustic wave acts as a traveling long-period grating. This is utilized to couple light from the lowest order to the first higher order optical modes of the PCFs. Factors affecting the acoustooptic coupling bandwidth are also investigated. In particular, the effect of axial variations in acoustooptic phase-mismatch coefficient are studied. In the second part of the thesis we use an electric field to control transmission properties of PCFs. Tunable photonic bandgap guidance is obtained by filling the holes of an initially index-guiding PCF with a nematic liquid crystal and applying an electric field. The electric field introduces a polarization-dependent change of transmission properties above a certain threshold field. By turning the applied field on/off, an electrically tunable optical switch is demonstrated. The third part consists of two theoretical works. In the first work, we use relativistic causality, i.e. that signals cannot propagate faster than the vacuum velocity of light, to show that Kramers-Kronig relations exist for waveguides, even when material absorption is negligible in the frequency range of interest. It turns out that evanescent modes enter into the Kramers-Kronig relations as an effective loss term. The Kramers-Kronig relations are particularly simple in weakly guiding waveguides as the evanescent modes of these waveguides can be approximated by the evanescent modes of free space. In the second work we investigate dispersion properties of planar Bragg waveguides with advanced cladding structures. It is pointed out that Bragg waveguides with chirped claddings do not give dispersion characteristics significantly different from Bragg waveguides with periodic claddings

Acoustooptic characterization of a birefringent two-mode photonic crystal fiber

The effect of axial variations in acoustooptic phase-mismatch coefficient of a two-mode birefringent photonic crystal fiber (PCF) is studied experimentally using two different methods. The first method is to determine axial non-uniformities directly from the transmission spectrum, while the second method is to use acoustic pulses. Both methods are seen to be in good agreement. It is found that axial non-uniformities increase the coupling bandwidth significantly as compared to an axially uniform fiber. The effect of acoustic birefringence is also considered

Optical limiting properties and z-scan measurements of carbon disulfide at 2.05 μm wavelength

Nonlinear and optical limiting properties of carbon disulfide (CS2) are characterized at 2.05 μm wavelength using a Q-switched Ho:YLF laser with high pulse energy. The nonlinear refractive index of CS2 is measured using the z-scan technique, giving a value of (1.9±0.5)·10−18  m2/W, i.e., (7.2±1.9)·10−12  esu, for the 25 ns pulses from the Ho:YLF laser. Self-focusing and dielectric breakdown in CS2 limited the output energy to 0.6 mJ in the optical limiting experiments for input energies of up to 150 mJ

Robust Identification of Concealed Dangerous Substances by Spectral Correlation of Terahertz Transmission Images

Terahertz images containing spectral information in each pixel are recorded in transmission mode using a fibercoupled time-domain spectroscopy system. The images are acquired by mounting a sample holder on an x–y stage, which is stepped across the beam in the two transverse directions, while the transmitted THz waveform is captured. The materials under investigation consist of uncovered and hidden samples of an explosive (RDX) and simulants (lactose and tartaric acid). Spectral angle mapping is used to identify the materials in the Terahertz images by comparing the spectrum in each pixel with a library of reference spectra for the different materials. We test the performance of several spectral characteristics derived from the measured transmission spectra. Robustness is studied by investigating the Receiver-Operating-Characteristics (ROCs). The ROCs are used to find which of the spectral characteristics is most robust to different sample preparation conditions, without the need for extensive pre-treatment of the data, such as baseline correction. Simple theoretical considerations are used to support the experimental results.This is the authors accepted and refereed manuscript to the article. © 2015 IEEE

Robust Identification of Concealed Dangerous Substances by Spectral Correlation of Terahertz Transmission Images

Terahertz images containing spectral information in each pixel are recorded in transmission mode using a fibercoupled time-domain spectroscopy system. The images are acquired by mounting a sample holder on an x–y stage, which is stepped across the beam in the two transverse directions, while the transmitted THz waveform is captured. The materials under investigation consist of uncovered and hidden samples of an explosive (RDX) and simulants (lactose and tartaric acid). Spectral angle mapping is used to identify the materials in the Terahertz images by comparing the spectrum in each pixel with a library of reference spectra for the different materials. We test the performance of several spectral characteristics derived from the measured transmission spectra. Robustness is studied by investigating the Receiver-Operating-Characteristics (ROCs). The ROCs are used to find which of the spectral characteristics is most robust to different sample preparation conditions, without the need for extensive pre-treatment of the data, such as baseline correction. Simple theoretical considerations are used to support the experimental results