Optical Image Amplification Research Articles

Optical image amplification in dual-comb microscopy

Dual-comb microscopy (DCM), based on a combination of dual-comb spectroscopy (DCS) with two-dimensional spectral encoding (2D-SE), is a promising method for scan-less confocal laser microscopy giving an amplitude and phase image contrast with the confocality. However, signal loss in a 2D-SE optical system hampers increase in image acquisition rate due to decreased signal-to-noise ratio. In this article, we demonstrated optical image amplification in DCM with an erbium-doped fiber amplifier (EDFA). Combined use of the image-encoded DCS interferogram and the EDFA benefits from not only the batch amplification of amplitude and phase images but also significant rejection of amplified spontaneous emission (ASE) background. Effectiveness of the optical-image-amplified DCM is highlighted in the single-shot quantitative nanometer-order surface topography and the real-time movie of polystyrene beads dynamics under water convection. The proposed method will be a powerful tool for real-time observation of surface topography and fast dynamic phenomena.

Improvement of an optical image by the measurement reduction technique at parametric multiplexing

In the process of parametric optical image amplification, images are formed at new frequencies in addition to the amplified original image. We show that the parametric multiplexing of optical images can be used to produce an image with improved quality. As an example, we study the parametric amplification of an optical image at low-frequency pumping in which multiplexed optical images turn out to be quantum-correlated. Additional improvement is made possible by using the information about the object that is available to the researcher, in particular, about sparsity of its image. To take the available information into account, we apply the measurement reduction technique.

Compact optical image amplifier pumped by a sub-nanosecond Nd:YAG microlaser

A compact sub-nanosecond optical image amplifier is proposed and demonstrated. It is pumped by an actively Q-switched diode-pumped Nd:YAG microlaser in virtue of the optical parametric amplification (OPA) technique and quasi-phase-matching scheme. Experimental results show that the optical image gain reaches 15.4 dB under a pump intensity of 15.3 MW/cm2. The influence of parametric fluorescence noise on the amplified image is obvious above 10 dB gain. The signal-to-noise ratio degradation of the amplifier image characterized by the noise figures is in sheer contrast with theoretical expectations. It shows that the experimental noise figure value reaches 2.2 dB, larger than the theoretical result of 0.7 dB at 15 dB gain.

Efficient optical image amplifier using periodically poled lithium niobate.

An efficient optical image amplification scheme has been proposed and demonstrated using the quasi-phase-matched optical parametric amplifier. Pumped with the 152 μJ per pulse pump laser at 532 nm, the input weak infrared image at 1064 nm with 3.5 pJ energy is amplified with a 55 dB optical gain using only a 3 mm long MgO-doped periodically poled lithium niobate (MgO:PPLN) crystal. A spatial resolution of 17 lines/mm on the surface of the PPLN crystal is obtained. Further numerical simulation indicates that our scheme enables efficient image enhancement with a long pulsed pumping source, such as nanosecond lasers.

Asymmetric-detection time-stretch optical microscopy (ATOM) for ultrafast high-contrast cellular imaging in flow

Accelerating imaging speed in optical microscopy is often realized at the expense of image contrast, image resolution, and detection sensitivity – a common predicament for advancing high-speed and high-throughput cellular imaging. We here demonstrate a new imaging approach, called asymmetric-detection time-stretch optical microscopy (ATOM), which can deliver ultrafast label-free high-contrast flow imaging with well delineated cellular morphological resolution and in-line optical image amplification to overcome the compromised imaging sensitivity at high speed. We show that ATOM can separately reveal the enhanced phase-gradient and absorption contrast in microfluidic live-cell imaging at a flow speed as high as ~10 m/s, corresponding to an imaging throughput of ~100,000 cells/sec. ATOM could thus be the enabling platform to meet the pressing need for intercalating optical microscopy in cellular assay, e.g. imaging flow cytometry – permitting high-throughput access to the morphological information of the individual cells simultaneously with a multitude of parameters obtained in the standard assay.

Performance of serial time-encoded amplified microscope

Serial time-encoded amplified microscopy (STEAM) is an entirely new imaging modality that enables ultrafast continuous real-time imaging with high sensitivity. By means of optical image amplification, STEAM overcomes the fundamental tradeoff between sensitivity and speed that affects virtually all optical imaging systems. Unlike the conventional microscope systems, the performance of STEAM depends not only on the lenses, but also on the properties of other components that are unique to STEAM, namely the spatial disperser, the group velocity dispersion element, and the back-end electronic digitizer. In this paper, we present an analysis that shows how these considerations affect the spatial resolution, and how they create a trade-off between the number of pixels and the frame rate of the STEAM imager. We also quantify how STEAM's optical image amplification feature improves the imaging sensitivity. These analyses not only provide valuable insight into the operation of STEAM technology but also serve as a blue print for implementation and optimization of this new imaging technology.

Image amplifier based on Yb^3+-doped multi-core phosphate optical fiber

We demonstrate image amplification with a 19-pixel optical image amplifier array based on high gain per unit length Yb(3+)-doped phosphate glass optical fiber. The 19 pixels of the image amplifier provide spatially uniform image amplification whose gain can reach 30 dB/pixel or more with a fiber length of 10 cm. This image amplifier responds quickly to changes in the image position - with potential for GHz-level frame rates. This unique approach for image amplification offers low noise, high gain, and wide field of view in a compact fiber-based device.

Parametric amplification and up-conversion of optical image in coupled nonlinear optical processes

We develop quantum theory of process of the parametric optical image amplification at high-frequency pumping which is accompanied by up - conversion one. Such interactions can be implemented by two coupled three-frequency optical processes. The theory developed takes into account the diffraction effect and the difference of group velocities of interacting waves. The expressions for mean photon numbers and noise figures of the interacting waves are obtained and the dependence of these parameters on the interaction length are examined.

Investigation and optimization of a pulsed ultraviolet image amplifier within a micro-marking system

We present an all optical image amplifier in the pulsed ultraviolet (355 nm) based on photorefractive two wave mixing and its implementation in an optical micro-lithographic system. Due to the high possible amplification factor it is possible to use masks with low damage threshold such as polymeric slides or an amplitude modulator based on liquid crystals. This leads to a versatile system which is independent of expensively prepared masks. The amplified image is de-magnified to the sub-millimetre range and projected onto the target. The main application for our system is the authentication of artifacts by imprinting an individual code onto the item surface.

Realization of an all optical image amplifier in the pulsed UV range and implementation to a micro-marking system

We report on the implementation of an all optical image amplifier by use of two wave mixing based on the photorefractive effect, within a micro-lithographic authentification system. The combination of a computer driven spatial light modulator and a holographic image amplifier enables the parallel engraving of information without the need of previously prepared masks. The necessity for an amplification of the information carrying beam rises from the damage threshold of the spatial light modulation device, which is lower than the energy density required for imprinting the information onto the objects surface. This work is embedded in a European Growth project, Holographic Authenticity Sensors, GRD1 –1999 –11078.

Phase-conjugating mirror with continuous-wave gain

We demonstrate a phase-conjugating mirror that has a continuous-wave power reflectivity much greater than unity (gain ~100). This mirror uses nonresonant degenerate four-wave mixing in a single crystal of barium titanate (BaTiO3). With our mirror we have (1) observed cw self-oscillation in an optical resonator formed by this mirror and a normal mirror, (2) demonstrated a cw oscillator that, in spite of phase-distorting material placed inside the resonator, will always emit a TEM00 mode, and (3) demonstrated an optical image amplifier. This mirror will work at any visible wavelength and with weak (milliwatt or weaker) pump beams.

Coherent optical image amplification by an injection-locked dye amplifier at 632.8 nm

Coherent amplification of images illuminated by the 632.8-nm radiation of He-Ne has been successfully demonstrated using a two-stage injection-locked pulsed dye amplifier technique. A gain of three times has been measured using Cresyl Violet 620 and Rhodamine B in ethanol, while maintaining signal bandwidth, relative phase, and direction, over a one-quarter μs pulse duration. A space bandwidth product of 500 000 was obtained by incorporation of the image amplifier into an optical image processing system.