Optical-parametric-amplification imaging of complex objects

Abstract

We used ultrafast Fourier-plane optical-parametric-amplification (OPA) imaging to simultaneously image, wavelength-shift, and amplify complex two-dimensional objects with spatial features from 1.1 to 11.3 line-pairs/millimeter, corresponding to a two-dimensional space-bandwidth product (SBP) of 13,790. This represents an increase in image complexity over previous analogous OPA imaging systems by almost three orders of magnitude. In wavelength-shifting the image from 930nm to an idler wavelength of 700nm, we observed image amplification by up to two orders of magnitude. OPTICAL-PARAMETRIC-AMPLIFICATION IMAGINGThe ultrahigh intensities available from ultrafast-laser technology allow access to a wide range of high-intensity phenomena and techniques. Whereas earlier laser systems required tightly focused beam spots in order to achieve sufficient intensities, recent advances in Ti:Sapphire regenerative amplifiers ("regens") allow high-intensity interactions of unfocused beams with relatively large diameters. Vastly improved stability in such systems also makes practical previously impractical highly nonlinear processes.Optical parametric amplification (OPA) 1 , in particular, which experiences gain that is an exponential of the pump-beam amplitude, benefits greatly from these technological advances. OPA has long been used to nonlinear-optically amplify weak input signals 2 , as well as to wavelength-convert them, usually from the infrared into the visible 3 . Unfortunately, due to its highly nonlinear nature, OPA is very sensitive to and severely limited by shot-to-shot jitter of the laser. Pulses that are too weak can yield no signal, and pulses that are too intense can yield undesirable background in the form of optical-parametric generation (OPG) or, worse, can damage the crystal. Such issues significantly complicate applications of OPA, and, as a result, OPA, perhaps more than any other optical process, benefits from the high intensity and, especially, the vastly improved shot-to-shot jitter of these laser systems.Indeed, the use of OPA for imaging applications (see Fig. 1) should benefit greatly. OPA imaging involves imaging an object (or target) with amplification and perhaps also simultaneous wavelength conversion, spatial-frequency filtering, time-gating and phase conjugation. An imaging system images or focuses the target onto a nonlinear medium, where an OPA pump beam amplifies (and potentially wavelength shifts and time-gates) it, and an additional imaging or focusing system transfers the image from the OPA medium to a camera (or free space propagation onto the camera results in phase-conjugation).The first demonstration of OPA imaging occurred in 1968, when Midwinter amplified and frequency-shifted an IR image to the visible 4, 5 . Since then, both monochromatic 6 and polychromatic 7 images have been amplified. When OPA is performed to amplify or frequency-shift an image, the interaction takes place between the signal and pump beams in the nonlinear medium, but different interaction planes can be used, dep...

Room-temperature mid-infrared single-photon spectral imaging

“…These results demonstrated the potential of the technology 19 . Cw upconversion in recent years 20,21,22,23 has not been directly used for infrared imaging, however waveguide single spatial mode upconverters has been used for infrared photon detection 24 . In upconversion spectroscopy low noise devices in the near infrared has been reported 25,26,27,28 Today, the preferred method for infrared spectroscopy is Fourier Transform Infrared spectroscopy (FTIR).…”

Parametric upconversion imaging and its applications

“…Note that the DFG and OPA based imaging are outside the scope of the present review, however the reader may consider these review articles [139], [188] for more details. The recent advances in DFG/OPA based imaging using different nonlinear crystals can also be found in [135], [189]- [193]. Researchers have also utilized second harmonic generation (SHG) for IR imaging.…”

Infrared up-conversion imaging in nonlinear metasurfaces

“…12 However, the low signal to noise ratio of CCD detectors and poor quality of nonlinear crystals at the time prevented practical developments of up-conversion imaging systems. Recently, the interest in such imaging systems has been renewed, driven by the availability of periodically-poled nonlinear crystals, [13][14][15] new laser sources [16][17][18] and the use of intra-cavity configurations, 14, 19 which can improve the performance of the systems. The main difficulty in the realization of these IR imaging systems is the phase-matching condition, which not only restricts the conversion efficiency of the up-conversion process but also limits the spectral bandwidth of the IR image, resolution and field of view.…”