Salman Noach

MICROFABRICATION OF AN ELECTROLUMINESCENT POLYMER LIGHT EMITTING DIODE PIXEL ARRAY

We describe a method to microfabricate a light emitting diode array with pixels based on conjugated electroluminescent polymers sandwiched between appropriate electrodes. This method, based on direct photoablation with the 193 nm emission of an excimer laser, maintains the properties of these unique polymers. The technique as described here has already achieved an array of 20 μm×20 μm pixels with enhanced electroluminescence (EL) from these pixels and possible spectral tuning of the EL by the application of varying external field. This method can be extended to achieve nanometer dimensionalities using near‐field nanolithography.

Design of a diffractive optical element for wide spectral bandwidth.

A new method for eliminating the chromatic aberration of a diffractive optical element (DOE) for wideband wavelengths is presented. The wideband-wavelength diffractive optical element (WBDOE) consists of two aligned DOEs. The use of different dispersive materials for the two DOEs eliminates chromatic aberration. The design and simulation of a WBDOE for the visible spectrum are presented.

Microfabrication of an electroluminescent polymer light emitting diode pixel array

Abstract We describe a method to miorofabricate a light emitting diode (LED) pixel array based on conjugated electroluminescent polymers sandwiched between ITO and aluminum. The method, based on direct photoablation using a 193 nm excimer laser, maintains intact the properties of the polymers. The technique as described here has already achieved array of 20μm × 20 μm pixels with enhanced electroluminescence (EL) from pixels. The method can be extended to achieve nanometer sizes using near-field nanolithography. The microfabrication of the LED array requires also the patterning of the ITO and the aluminum electrode. For better performance of the device it is important to map the conductivity of the patterned electrodes, For that purpose we have used a novel mm-wave conductivity microscope which is capable to measure the local conductivity of the patterned film with a spatial resolution of ~10–30 p.m.

Design of diffractive optical elements for multiple wavelengths

A method for producing diffractive optical elements (DOEs) for multiple wavelengths without chromatic aberration is described. These DOEs can be designed for any distinct wavelength. The DOEs are produced from two different optical materials, taking advantage of their different refractive indices and dispersions.

Integrated diffractive and refractive elements for spectrum shaping

Diffractive elements can be designed for spectrum shaping in the Fourier or Fresnel plane by iterative methods. It is necessary to use a Fourier lens and the wavelength for which the diffractive elements were designed to get the required spectrum shaping at the Fourier plane. Using a different wavelength will cause chromatic aberration. We deal with the combination of refractive and diffractive elements and two or more different diffractive elements on the same element to get appropriate beam shaping of light sources with a multiple spectral output. Simulations are preformed that transform the profile of a He-Ne laser with a Nd:YAG laser source, and shape the trapezoidal beam profile of an excimer laser into a Gaussian beam is also considered.

Diode end-pumped passively Q-switched Tm:YAP laser with 1.85-mJ pulse energy.

Passive Q switching of a Tm:YAP solid-state laser at 1935 nm with Cr:ZnSe and Cr:ZnS polycrystalline saturable absorbers is demonstrated for the first time, to the best of our knowledge. With Cr:ZnS, a maximum pulse energy of 1.85 mJ is obtained for a pulse duration of 35.8 ns, resulting in a peak power of 51.7 kW. With Cr:ZnSe, the achieved pulse energy of 1.55 mJ with a pulse duration of 42.2 ns leads to 36.7-kW peak power. These high pulse energies, together with the unique lasing wavelength at 1935 nm, make this laser a promising tool for biomedical and microsurgery applications.

Wave-front control and aberration correction with a diffractive optical element.

A method that permits aberration correction and wave-front reshaping with a diffractive optical element (DOE) is described. Two aligned DOEs made of two different dispersive materials are used. The different dispersions of the two materials in addition to freedom in choosing their thicknesses enables the chromatic aberration and the wave fronts to be manipulated. Design and simulation of such DOEs are described.

Calibration-Free Pulse Oximetry Based on Two Wavelengths in the Infrared — A Preliminary Study

The assessment of oxygen saturation in arterial blood by pulse oximetry (SpO2) is based on the different light absorption spectra for oxygenated and deoxygenated hemoglobin and the analysis of photoplethysmographic (PPG) signals acquired at two wavelengths. Commercial pulse oximeters use two wavelengths in the red and infrared regions which have different pathlengths and the relationship between the PPG-derived parameters and oxygen saturation in arterial blood is determined by means of an empirical calibration. This calibration results in an inherent error, and pulse oximetry thus has an error of about 4%, which is too high for some clinical problems. We present calibration-free pulse oximetry for measurement of SpO2, based on PPG pulses of two nearby wavelengths in the infrared. By neglecting the difference between the path-lengths of the two nearby wavelengths, SpO2 can be derived from the PPG parameters with no need for calibration. In the current study we used three laser diodes of wavelengths 780, 785 and 808 nm, with narrow spectral line-width. SaO2 was calculated by using each pair of PPG signals selected from the three wavelengths. In measurements on healthy subjects, SpO2 values, obtained by the 780–808 nm wavelength pair were found to be in the normal range. The measurement of SpO2 by two nearby wavelengths in the infrared with narrow line-width enables the assessment of SpO2 without calibration.

High pulse energy passive Q-switching of a diode-pumped Tm:YLF laser by Cr:ZnSe

A passively Q-switched diode-pumped Tm:YLF laser with polycrystalline Cr:ZnSe as the saturable absorber is demonstrated for the first time, to the best of our knowledge. By using saturable absorbers with different initial transmission, the maximum pulse energy reached 4.22 mJ with peak power of 162.3 kW for a pulse duration of 26 ns. The maximum output average power amounted to 2.2 W. These results constitute significant improvement from the highest average power, pulse energy and peak power results for the PQS Tm:YLF laser to date.

Achromatic diffractive optical element

A new method for solving the dispersion problem of Diffractive Optical Elements (DOEs) is suggested. By aligning two DOEs made of different dispersive materials, the optical path differences as a function of the wavelength can be controlled. Applying this concept, a combined achromatic DOE can be designed for applications that require wavefront control using different wavelengths or wideband light sources. Numerical and simulation results are presented.