Mirror Illumination Research Articles

Development of soft X-ray ptychography and fluorescence microscopy system using total-reflection wolter mirror and application to measurement of drug-treated mammalian cells

We developed a soft X-ray microscopic imaging system, CARROT, that combines ptychography and fluorescence X-ray microscopy using a total-reflection Wolter mirror illumination system. The system offers advantages such as achromaticity and long working distances, enabling seamless application to a wide wavelength range. We demonstrated high-resolution imaging of cellular structures and sub-micrometer-scale changes induced by drug administration in mammalian cells. We further showcased the capability to seamlessly switch from ptychography measurements to X-ray fluorescence measurements at different wavelengths to map elemental distributions within cells. Our findings suggest that this system can be used for investigating the correlation between intracellular structures and elemental distribution, as well as for multimodal measurements of visible light fluorescence, Raman scattering, and soft X-rays to provide valuable insights into understanding intracellular dynamics.

On the emission of radiation by an isolated vibrating metallic mirror

Quantum electrodynamics predicts the appearance of radiation in an empty cavity in which one of the mirrors is vibrating. It also predicts the appearance of radiation from an isolated vibrating mirror. Such effects can be described within the framework of classical electrodynamics. We present the qualitative explanation of the effect, along with the results of numerical simulation of the emission of radiation by an isolated vibrating metallic mirror, which can be induced by mirror illumination by an ultrashort pulse of light. The dynamics of conduction electrons in the metallic mirror is described by the classical Drude model. Simulation was performed for the cases of mirror illumination by either a bipolar or a unipolar pulse.

Novel illumination system of synchrotron radiation stepper with full field exposure method

We estimate the pattern distortion and the critical dimension (CD) variation due to the thermal distortion under a large exposure field for the full field exposure method. We verify that the effect of the thermal distortion of the mask and wafer on the pattern distortion and the CD variation is small enough under the condition of mass production of devices of 0.1 μm design rule. We present a design of the novel two mirror illumination system which can improve the throughput both by exposing a field as large as 50 mm square and by condensing synchrotron radiation (SR) spread in the horizontal plane. The effects of the variation of the position of the SR source and the mirrors and the size of the SR source on the performance of the stepper are investigated.

Determination of the heat transfer capability of laser mirrors with cooled cells

A mathematical model of steady-state heat transfer in a laser mirror involving cooled prismatically shaped cells has been developed. Using cooling systems with hexahedral and tetrahedral cells (by the number of side walls) as examples, the influence of the mirror illumination nonuniformity, reflector thickness, and other parameters on the effective heat-transfer coefficient and thermal head coefficient is investigated; the physical limits for heat-transfer characteristics in the case of an unlimited increase in heat transfer from the surfaces of the cell walls have been determined.

Light-integrating cylinder for inertial confinement fusion light balance measurements in mirror illumination systems

This report describes the design and operation of a diagnostic instrument used for light balance measurements in inertial fusion experiments. The instrument is a light-integrating cylinder that uses the integrating principles of the Ulbricht sphere, but which was designed to operate in a reflective illumination environment. The cylinder has been used to make measurements with both high-absorption disk targets and low-absorption foil targets, illuminated with 20–80 J of green (527-nm) light. We have also modeled the cylinder to determine its theoretical integrating performance under a variety of operating conditions. Initial sensitivity was measured at 0.4 V/J and degraded over target shot number to about 0.25 V/J. The instrument has a measurement accuracy of 10% for scattered light and an absorption measurement accuracy of 10% for strongly absorbing targets, and 30%–70% for weakly absorbing targets.

Mirror Deformations and Wavefront Aberrations Caused by C.w. High Power Laser Beams

The thermal deformation of a metallic mirror used for focusing on or simply directing a laser beam to a workpiece is investigated. The displacement of the front surface is evaluated by using a rapidly converging Dini series. The effects of the distortion on the peak intensity of a focal spot are evaluated by using the normalized intensity function i(P) as a performance figure. Expanding the distorted mirror aberration function in a series of Zernike polynomials, the dependence of i(P) on the mirror illumination and physical parameters is assessed. The results of many calculations illustrate the potential of this analysis.

Study of intensity pulsations in proton-bombarded stripe-geometry double-heterostructure AlxGa1−xAs lasers

The pulsations in the laser emission from several lasers have been studied as a function of temperature, cavity length, external mirror illumination, and effect of mirror etching. Selected DH lasers with 12-μm-wide stripes delineated by proton bombardment and 380-μm-long cavities were used. The modulation depth of the pulsations at 300 °K increases approximately linearly with current above a threshold value and becomes fully modulated at high output powers. At intermediate temperatures, the modulation exhibits a similar initial slope but is not complete at the highest measured output. At low temperatures, well-developed pulsations are not observed; the modulation reaches a maximum at a low amplitude level and then decreases. The frequency dependence of the pulsations indicates that when the modulation level is increasing, the frequency f is relatively constant, and above the maximum moduation f 2 increases approximately linearly with output power. The dependence on cavity length was studied using a series of 380-μm-long unbonded chips which showed strong pulsations under pulsed operation and were then cleaved into ∼125-μm-long sections. Of the short devices which lased, both center and end segments showed pulsations, indicating that unpumped end regions are not acting as saturable absorbers, resulting in the pulsations. The effects of illuminating the mirrors with 4880- and 6328-Å laser radiation and injecting 1.06-μm radiation into the active region were studied. Illuminating the mirrors increased the threshold and decreased the external differential quantum efficiency. The pulsations had the same light power threshold and had qualitatively the same dependence on output power. The possibility that an oxide layer over the facet is associated with the pulsations was studied by stripping the oxide with a dilute NH4OH solution. Up to four 5-sec strippings did not appreciably affect the pulsations. Hence, oxide layers and related nonradiative centers at the mirrors are not responsible for pulsations. Most lasers had kinks in the L-I characteristic. The pulsations were quenched if the lasers were operated in a region near the kink. The models used previously to describe the pulsations do not appear to apply to the lasers studied here. Much of the pulsation behavior can be explained by a simple nonlinear-gain model in the electron-photon density equations of the laser. Such a nonlinear gain can result from spatial nonlinearities in the gain within the stripe.

Comment on resonant absorption

An average over angles of incidence of the usual resonant absorption function is presented. This form is appropriate under experimental conditions where the angles of incidence vary greatly and in an unknown manner. For comparison a lens-ellipsoidal mirror illumination system with a known longitudinal aberration is considered. In the latter example the angles of incidence are readily obtained and the resulting resonance absorption function evaluated. The associated magnetic fields are calculated in a similar fashion.

Output coupling for closely confined Pb<inf>1-x</inf>Sn<inf>x</inf>Te double-heterostructure lasers

The output coupling of an idealized, symmetric model of a double-heterostructure (DH) laser is analyzed theoretically using parameters suitable to Pb 1-x Sn x Te. For the TE O mode incident at the laser mirror and for thin optical guiding regions such that only the TE O , TE 1 , TM O , and TM 1 modes may propagate, an exact formulation of the coupling problem is obtained including mode coupling at the mirror into the continuum of unguided radiation modes. Using this formulation, the power reflection and transmission coefficients, the fraction of incident power coupled into the radiation modes, the mirror illumination, and the far-field pattern are calculated for typical parameters. Significant mode coupling can occur, limiting the maximum external efficiency of such lasers. This and other potentially undesirable characteristics resulting from close optical confinement, such as large output beam divergence, must be considered in design criteria for DH structures in this alloy system.

Stripe-geometry Pb<inf>1-x</inf>Sn<inf>x</inf>Te diode lasers

In order to avoid parasitic modes that frequently occur in conventional rectangular lead-chalcogenide diode laser structures, stripe junction lasers emitting at about 11 μm at 4.2 K have been fabricated from vapor-grown Pb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.88</inf> Sn <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.12</inf> Te. Measurements of spectra, polarization, mirror illumination patterns, and far-field patterns provide conclusive evidence that these lasers emit in a fundamental spatial transverse mode. The emission spectra of the stripe lasers consist of regularly spaced modes corresponding to the longitudinal cavity with an effective index of refraction of 7.1. The measured width of the emitting region closely corresponds to the junction width both for the 50- and 100- μm-wide stripe lasers used. The depth of the emitting region perpendicular to the junction plane was measured to be approximately 50 μm in all of the lasers. As <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> S <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> dielectric coatings of various optical thicknesses have been sequentially applied to one end face in order to evaluate the gain and loss parameters of the active region from the threshold variation with reflectivity. Loss parameter values of 12-54 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , gain parameter values of 0.084-0.24 cm/A, and internal quantum efficiencies of 0.013-0.055 are deduced from these measurements. In addition, the antireflection coating produced as much as a fourfold increase in output power at currents above threshold.

Resonant modes of GaAs junction lasers - III: Propagation characteristics of laser beams with rectangular symmetry

In Parts I and II of this work [1], [2], the resonant modes of GaAs lasers, as predicted from a proposed model, are found to be in very good agreement with experimental results that emphasize the frequency domain. This paper, Part III, supplements the previous work by investigating the spatial field distributions of junction-laser beams. For the first time, the propagation characteristics of the beams are described mathematically in a manner that is consistent with detailed beamwidth measurements in the Fresnel and Fraunhofer regions of the diffraction field. This correlation between theory and experiment is made possible by the use of a lens-slit combination that ensures the generation of reproducible beams with rectangular symmetry. The astigmatic beam solutions describing the propagation characteristics beyond the slit include beam-broadening effects produced both by the lens and by phase variations at the laser mirror, along the junction plane. These latter variations have not been previously reported. Their existence is deduced from our measurements beyond the slit, which show a greater beam expansion along the junction plane than can be theoretically accounted for by the lens system alone. Near threshold, at a distance of one beamwidth from the center of the mirror illumination, the phase lag is found to have a current-dependent magnitude of a few degrees.

GAUSSIAN BEAMS FROM GaAs JUNCTION LASERS

Gaussian beams have been obtained from a GaAs junction laser operating in conjunction with a microscope objective and a slit. The laser mirror illumination, as viewed in the image plane of the objective, is asymmetric perpendicular to the junction plane and consists of a primary intensity maximum along with several weaker secondary peaks. The slit, placed in the image plane, suppresses the secondary peaks thereby eliminating their effects in the diffraction field. The isolated primary maximum is approximately Gaussian shaped and the radiation emanating from the slit retains its Gaussian profile as it propagates into the far-field region.