Eran Tal

Scanningless depth-resolved microscopy.

The ability to perform optical sectioning is one of the great advantages of laser-scanning microscopy. This introduces, however, a number of difficulties due to the scanning process, such as lower frame rates due to the serial acquisition process. Here we show that by introducing spatiotemporal pulse shaping techniques to multiphoton microscopy it is possible to obtain full-frame depth resolved imaging completely without scanning. Our method relies on temporal focusing of the illumination pulse. The pulsed excitation field is compressed as it propagates through the sample, reaching its shortest duration at the focal plane, before stretching again beyond it. This method is applied to obtain depth-resolved twophoton excitation fluorescence (TPEF) images of drosophila egg-chambers with nearly 105 effective pixels using a standard Ti:Sapphire laser oscillator.

Improved depth resolution in video-rate line-scanning multiphoton microscopy using temporal focusing

By introducing spatiotemporal pulse shaping techniques to multiphoton microscopy it is possible to obtain video-rate images with depth resolution similar to point-by-point scanning multiphoton microscopy while mechanically scanning in only one dimension. This is achieved by temporal focusing of the illumination pulse: The pulsed excitation field is compressed as it propagates through the sample, reaching its shortest duration (and highest peak intensity) at the focal plane before stretching again beyond it. This method is applied to produce, in a simple and scalable setup, video-rate two-photon excitation fluorescence images of Drosophila egg chambers with nearly 100,000 effective pixels and 1.5 microm depth resolution.

Depth-resolved structural imaging by third-harmonic generation microscopy

Third harmonic generation microscopy is shown to be a robust method for obtaining structural information on a variety of biological specimens. Its nature allows depth-resolved imaging of inhomogeneities with virtually no background from surrounding homogeneous media. With an appropriate illumination geometry, third harmonic generation microscopy is shown to be particularly suitable for imaging of biogenic crystals, enabling extraction of the crystal orientation.

Femtosecond pulse-shape modulation at nanosecond rates.

We report high-rate, computer-controlled femtosecond pulse shaping by use of an electro-optical gallium arsenide optical phased-array modulator with 2304 controlled waveguides. It provides fast modulation speed of both spectral phases and amplitudes. Limited by the driving electronics of our current setup, we were able to update a pulse shape in approximately 30 ns. This technique paves the way toward individual shaping of every single pulse of typical femtosecond mode-locked oscillators.

Depth-resolved multiphoton polarization microscopy by third-harmonic generation

We achieve depth-resolved polarization microscopy by measuring third-harmonic generation induced by a tightly focused circularly polarized beam. In crystals exhibiting strong birefringence this signal is dominated by positively phase-matched third-harmonic generation. This process occurs in only optically anisotropic media, in which the birefringence compensates for the phase mismatch between the fundamental and the third harmonic induced by dispersion. Both the intensity and the polarization of the emitted signal provide information on the local optical anisotropy. We demonstrate the technique by imaging biogenic crystals in sea urchin larval spicules.

Improving the efficiency of an optical parametric oscillator by tailoring the pump pulse shape

The conversion efficiency of an optical parametric oscillator is reduced by energy consumption during build-up of signal and idler intensities and due to back-conversion effects. By tailoring the pump pulse temporal shape, we are able to improve the conversion efficiency by minimizing build-up time and back-conversion. Simulations predict a significant improvement in 1064 nm to 4000 nm idler conversion by using a double-rectangular temporal shape rather than using a simple Gaussian pulse. Experimental results qualitatively verify the effect resulting in a 20% improvement of a rectangular pulse over a Gaussian pulse.

Transformation from an ultrashort pulse to a spatiotemporal speckle by a thin scattering surface.

We have theoretically and experimentally studied the local temporal and spectral characteristics of an ultrashort pulse passing a simple thin diffusive element. We show that as one moves away from the diffuser the pulse evolves into a spatiotemporal speckle.

Forty years of lasers at ELOP–Elbit Systems

Lasers and laser systems are a mature technology, yet there is a long road ahead for innovation and enthusiasm. We review some of the 40 years of R&D and manufacturing of lasers at ELOP-Elbit Systems. Bulk solid state lasers, for designators and range finders, as well as fiber lasers, for directed IR countermeasures and laser radar applications are described. These two technologies provide and will continue to offer a vast number of products for security and defense applications. Current and future generations of laser products will have higher average power together with improved beam quality, better efficiencies, and superior robustness all in a more compact package.

Intelligent switches of integrated lightwave circuits with core telecommunication functions

We present a brief overview of a promising switching technology based on Silica on Silicon thermo-optic integrated circuits. This is basically a 2D solid-state optical device capable of non-blocking switching operation. Except of its excellent performance (insertion loss<5dB, switching time<2ms...), the switch enables additional important build-in functionalities. It enables single-to- single channel switching and single-to-multiple channel multicasting/broadcasting. In addition, it has the capability of channel weighting and variable output power control (attenuation), for instance, to equalize signal levels and compensate for unbalanced different optical input powers, or to equalize unbalanced EDFA gain curve. We examine the market segments appropriate for the switch size and technology, followed by a discussion of the basic features of the technology. The discussion is focused on important requirements from the switch and the technology (e.g., insertion loss, power consumption, channel isolation, extinction ratio, switching time, and heat dissipation). The mechanical design is also considered. It must take into account integration of optical fiber, optical planar wafer, analog electronics and digital microprocessor controls, embedded software, and heating power dissipation. The Lynx Photon.8x8 switch is compared to competing technologies, in terms of typical market performance requirements.

Space multiplexed multiphoton microscopy by temporal focusing of ultrashort pulses

The ability to perform optical sectioning is one of the great advantages of laser-scanning microscopy. This introduces, however, a number of difficulties due to the scanning process, such as lower frame rates due to the serial acquisition process. Here we show that by introducing spatiotemporal pulse shaping techniques to multiphoton microscopy it is possible to obtain full-frame depth resolved imaging completely without scanning. Our method relies on temporal focusing of the illumination pulse. The pulsed excitation field is compressed as it propagates through the sample, reaching its shortest duration at the focal plane, before stretching again beyond it. Combining temporal focusing with line-scanning microscopy results in an enhanced depth resolution, equivalent to that achieved by point scanning. Both the scanningless and the line-scanning techniques are applied to obtain depth-resolved two-photon excitation fluorescence (TPEF) images of drosophila egg-chambers.