Absorption Loss Measurements Research Articles

Absorption loss properties and Stokes shifts of InGaAs-based self-assembled well-wire-hybrid quantum structures

Stokes shift is an important physical property relating to emission and absorption of light-emitting diodes, which reflects photon self-absorption situation and affects the device performance. Nowadays, it is becoming more and more difficult to change Stokes shift and relevant physical properties to further improve device performance with traditional quantum structures from increasing requirements in application. Therefore, hybrid quantum structures have attracted an attention recently. However, the properties related to Stokes shift in the new configurations have not been revealed so far. In this paper, we investigate the absorption loss and Stokes shift of the newly proposed InGaAs self-assembled well-wire-hybrid quantum structure. By designing a new absorption loss measurement approach, we can conveniently extract internal optical mode loss of a quantum structure and explore its Stokes shift with the measured absorption spectra. Our findings reveal that the presence of quantum wires in the structure can significantly reduce the Stokes shift difference between transverse electric and transverse magnetic (TM) polarizations from 66.7% for a traditional quantum well to 15.4%. It suggests the potential for the reduction of TM-mode photon self-absorption in a compressive-strain quantum structure. This phenomenon offers new prospects for the development of polarization-insensitive devices.

Light Scattering from Rough Silver Surfaces: Modeling of Absorption Loss Measurements.

We consider two series of experimental setups of multilayered Ag/ZnO thin films with varying surface morphologies given by atomic force microscopy images. The absorption loss under diffuse scattering is studied theoretically by applying a combination of the scattering matrix approach with diffraction theory for randomly nanotextured interfaces. Our modeling is in excellent agreement with the respective measurements. The theoretical approach is applicable to a wide range of wavelengths, surface morphologies, and materials for both measured and computed rough surface morphologies.

Analysis on absolute measurement of optical coating absorption loss based on photothermal detuning technique

Based on the photothermal detuning technique, the three linear relations among reflectance (or transmittance), temperature rise, and pump beam power are studied to achieve the absolute measurement of absorption loss. The relation between temperature and reflectance and the calculation accuracy of temperature rise on sample surface have great impacts on the measured result. The influences of parameters involved in the method and the relation between temperature and reflectance and the temperature model of sample surface are also studied. The results show that the absolute absorption loss of optical coatings can be achieved by the proposed method. The measurement accuracy depends on the temperature model and the relation between temperature and reflectance. The linear relation between reflectance and temperature rise has largest slope when probe beam wavelength is 632.8 nm and incident angle is 28o. The linear relation slope between temperature rise and pump beam power decreases with the growing of beam size and modulation frequency. The results provide theoretical and experimental supports for the perfection and further application of the photothermal detuning technique.

Study on the Spatial Resolution of Imaging Technique for Absorption Loss Measurement of Optical Coatings

The uniformity of optical coatings becomes more and more important as large diameter optical devices are widely used. Absorption loss in optical components, particularly in optical coatings, is a limiting factor in high-power laser applications. This article analyzes the main factors, which affect the spatial resolution of three techniques for surface absorption loss measurement, including the photothermal deflection technique, the surface thermal lens technique, and the photothermal detuning technique. The influence of the size of the heating and probe beam on the photothermal detuning technique is studied in detail. Experiments are conducted to study the photothermal signal of the photothermal detuning technique for absorption measurement of the optical coating point by point. The results show that the main factors, which affect the spatial resolution of imaging measurements for absorption loss of coatings, are the heating beam size and the step accuracy of the sample translation stage. The heating and probe beam sizes has a significant impact on the application of the photothermal detuning technique. Experimental result shows that the photothermal detuning technique can be used for imaging of absorption loss measurements of optical coatings. The results provide theoretical and experimental supports for further application of the photothermal detuning technique.

Investigation on an evanescent wave fiber-optic absorption sensor based on fiber loop cavity ring-down spectroscopy

An improved ring-down measurement principle for optical waveguides is presented. Fiber loop ring-down spectroscopy allows for measurement of minute optical losses in high-finesse fiber-optic cavities and immunity to the fluctuation of laser source. The evanescent wave absorption losses dependent on the absorption and the refractive index of ambient solution have been theoretically analyzed. The complex refractive index is introduced into our model and extinction coefficient can be calculated accurately through finite element analysis by setting the boundaries of the fiber and the ambient conditions. Using this method, the refractive index of environment can be taken into consideration. Our principle is validated by the highly-sensitive measurement of evanescent wave absorption loss. By chemically processing the surface of sensing segment along an extending ring-down cavity, the concentration of small volume Diethyl Sulphoxide solution where the etched fiber immersed into has been successfully measured and discussed.

Measurement of Absorption Loss at 80 kHz Band for Wideband Underwater Acoustic Communication

To achieve high-speed acoustic data transmission, the use of a frequency band of 80±20 kHz is being considered. However, the absorption attenuation coefficient in these frequencies only has empirical formula. Therefore, the absorption attenuation was measured using the frequency of 60 to 100 kHz within the propagation distance of 250 to 510 m at a 1,000 m depth. The transmission signal wave form was measured with conductivity, temperature, and depth (CTD) data. From these measured data, the absorption attenuation coefficient was calculated using several empirical equations. As a result, a corresponding comparatively good for the empirical formula of Francois and Garrison.

Cooperative luminescence and absorption in ytterbium doped aluminosilicate glass optical fibres and preforms

The cooperative luminescence and absorption properties of Yb 3+ doped aluminosilicate glass optical fibres and preforms are investigated in detail. In accordance with previous investigations, both the visible cooperative luminescence and the infrared luminescence decay measurements have been resolved into a single exponential decay component. We show that for a glass with similar Yb 3+ dopant concentration but more Al 3+, the glass emits less visible luminescence. Absorption loss measurements completed on fibre samples revealed a broad absorption in the 350–500 nm range, which we propose is due to a combination of Yb 2+ absorption and cooperative absorption from Yb 3+ ion pairs.

3-11-01 A Measurement of Absorption Loss at 80 kHz Band(Underwater ultrasound)

3-11-01 A Measurement of Absorption Loss at 80 kHz Band(Underwater ultrasound)

New techniques for optical absorption measurement of implanted nanoparticles in float glass

New techniques are reported for optical absorption and waveguide loss measurement of copper, gold and silver implanted float glass. Implantations were carried out on the tin face of the float glass since this face is an optical waveguide. Specially made triangle shape masks were used during implantation to study the optical loss–implant length relation. Absorption coefficients were extracted as 2.4 and 1 cm −1 for the gold and silver implants at 633 nm, respectively. These values were found to be implant condition dependent. To analyse the shape of nanoparticles a sandwiched structure was used in an optical absorption measurement set-up in which two guiding faces were put in contact. The sandwiched structure places the colloids at the centre of the optical field distribution rather than on the boundary zone. These experiments have revealed that the copper and the gold particles may have non-spherical shapes, whereas for silver, the formation of spherical nanoparticles is more likely.

Homoarginine Labeling is Suitable for Determination of Protein Absorption in Miniature Pigs

Intestinal proteolysis and absorption of dietary protein was followed using a chemical label of the lysine side-chain. Protein-bound lysine was transformed into homoarginine (HA), an amino acid that is not used for protein synthesis. Disappearance in the intestinal tract of HA originating from labeled casein and soybean isolate and appearance in peripheral blood was followed in four miniature pigs fitted with permanent T-cannulas at the proximal jejunum and ileum. Less than 0.2% of HA appeared in the digesta at the ileum when up to 13.5 mmol of HA was infused either into the jejunum or jugular vein. Several factors suggest that HA in fact traces the exogenous (dietary) protein: 1) the quick postprandial appearance of HA in plasma; 2) the high (greater than 97%) oro-ileal absorption of HA-labeled casein and soybean isolate; 3) the similarity of chymotryptic proteolysis in vitro of guanidinated and native casein; 4) the fact that only trace amounts of the marker reenter the intestinal lumen from the blood. Therefore HA-label is suitable for the differentiation of exogenous and endogenous protein in the chyme and thus the measurement of oro-ileal protein absorption and irreversible loss of endogenous protein in the chyme of the small intestine.

Proposed method for measurement of absorption loss and beam efficiency of large mm-wave reflector antennas in compact antenna test range by using hot and cold loads

A novel method to measure absorption loss and beam efficiency of large reflector antennas at millimetre wave frequencies is presented. It is based on a compact antenna test range (CATR) which has hot and cold loads placed at the focal plane. The size of loads is feasible. If the measurements are carried out without a CATR, the loads are difficult or impossible to realise. An analysis of the measurement of a 2 m antenna, using a lownoise receiver, shows that the accuracy is better than ±0.1 dB for the loss and ±1% for the beam efficiency.

Optical fibre absorption loss measurement using a pyro-electric poly(vinylidene fluoride) tube

The authors present a calorimetric technique using a pyroelectric PVDF tube sensor for measuring absorption loss in optical fibres. They show theoretically that the sensitivity could be of the order of 0.005 dB km-1 with a measurement time of about 19 s. Measurements made on single-model fibre at 1.06 microns show that absorption loss is about 0.2 dB km-1. They also present data on the components which contribute to the total loss. Extrapolation of measurements indicate that absorption effects make up approximately 0.1 dB km-1 at 1.55 mu m.

Characterization of single-mode optical fibres

Experimental techniques for the measurement of total loss and absorption loss, chromatic and monochromatic bandwidth, mode cut-off and refractive index profile are reviewed and illustrated by the results obtained on a particular single-mode fibre. The relationship between theory and experiment is explored.

Absorption loss and photorefractive-index changes in Ti:LiNbO_3 crystals and waveguides

Measurement of optical absorption loss and photorefractive sensitivity (optically induced index changes) in Ti-diffused waveguides and bulk Ti-doped single crystals are reported. The absorption loss of strip guides is found to be 0.3 dB/cm at 0.633 microm, and this is expected to decrease at longer wavelengths. The results demonstrate that Ti impurities do not contribute to the absorption loss or to the photorefractive-index changes directly, rather these parameters are determined by impurities in the substrate crystal. A simple pyroelectric method for electrical adjustment of the optical input coupling is also reported.

Higher-lying singlet states of poly-n-vinylcarbazole: A CNDO/S study

The CNDO/S technique has been used to study the higher-lying singlet states in poly-N-vinylcarbazole PVK. This study finds correlations with features observed in optical absorption and electron energy loss measurements.(AIP)

Radiation Effects in Synthetic Quartz: The Role of Electrodiffusion and Radiation-Induced Mobility of Interstitial Ions

Interstitial ions, both alkalis and hydrogen, have been shown to play a crucial role in the radiation response of high-quality commercially-available quartz. Electron spin resonance (ESR), infrared absorption (IR), and acoustic loss (Q-1) measurements have been made on various samples, swept and unswept, cut from Sawyer and Toyo material. These measurements have shown that the number and nature of irradiation-induced defects depend strongly on the irradiation temperature and previous sweeping treatments. In unswept samples, interstitial alkalis are initially trapped adjacent to substitutional Al3+ ions but become mobile if the irradiation temperature is above 200 K. In swept samples, the interstitial alkalis are replaced by hydrogen, in the form of OH- molecules, and irradiation at temperatures as low as 77 K causes the hydrogen to become mobile. The substantial difference in temperature for onset of the radiation-induced mobility of the alkali and hydrogen interstitial ions forms the basis of a sensitive method for testing completeness of the sweeping process.

Measurements of sound power, sound absorption, and sound transmission loss in the reverberant rooms of the Royal Melbourne Institute of Technology

The new reverberant rooms are described. They consist of a single room of 200 m3 volume which is employed for sound power and sound absorption measurements and a smaller coupled pair of rooms each of approximately 110 m3 volume used for measurement of sound transmission loss. Each room is of 30 cm reinforced concrete and vibration isolated from the main building structure. The floor plans are pentagonal, the ceilings are inclined, and some of the walls are tilted from the vertical. For the large room without absorbers or any type of diffusing element, the reverberation time is 10 s at 500 Hz. The spatial variations of the sound field and of the reverberation times are described, together with preliminary results on the measurement of sound power, sound absorption, and sound transmission loss.

Homogeneously broadened CW lasers with uniform distributed loss

The exact equations relating the CW output power to the parameters of a homogeneously broadened laser with distributed loss and its cavity are analytically intractable. In their place, simple approximate expressions are derived which permit convenient evaluation of the laser parameters from output power measurements in cavities with variable coupling, and conversely, of the maximum available oscillator power from small-signal gain and absorption-loss measurements. The approximate solutions have negligible error for lossy standing-wave lasers and are but slightly less accurate for lossy traveling-wave ring lasers.

Effect of impurity aggregation on the thermoluminescent decay of X-irradiated KCl:Sr2+

The effect of thermal treatment on the thermoluminescence peaks of X-ray irradiated KCl:Sr2+ and their isothermal decay have been investigated. A new characteristic decay behaviour has been found for the curves of the main peak (408K). It is shown to be sensitive to impurity aggregation which can be dispersed by thermal treatment at 393K. From the optical absorption and dielectric loss measurements, it is suggested that interstitial traps are responsible for the decay behaviour. A quantitative explanation of the decay behaviour is obtained by using rate equations based on the two types of the trapping centre of interstitials. An emission band at 430 nm was observed, its spectrum being unchanged by thermal treatments.

TM Spectra: A Measure of Diffuseness of Reverberant Sound

Diffuseness of reverberant sound is a sine qua non for accurate reverberation room measurement of sound absorption, power, and transmission loss. Most authorities regard it as important for the concert hall as well. And yet, technique for the measurement of diffuseness is not well developed. In this connection, the recently proposed technique of TM (traversing microphone) spectroscopy shows promise. The technique exploits information on diffuseness contained in the spatial correlation function of instantaneous sound pressure. Mathematically, the TM spectrum is the Fourier transform of the spatial correlation function. Physically, it can be interpreted as the power spectrum obtained at the terminals of a small microphone traversing the room at constant speed. For an ideally diffuse field of narrow bandwidth, the TM spectrum is, conveniently, a perfect rectangle. For a less diffuse field, deviations from the rectangular shape will occur. Supporting experimental and analytical results are shown. The limitations and promise of this new technique are discussed. [This work supported by the Office of Naval Research, Code 468.]