In this paper, we will present our preliminary results on our development of infrared and terahertz generation by ultrafast laser pulses. The objective of this project is to develop (i) portable and cost effective spatially coherent broadband Infrared (IR) and Terahertz (THz) illuminating light sources. To effectively generate spatially coherent broadband IR and THz sources, we use a novel nonlinear optical technical approach by harnessing the huge nonlinear effect of the specially designed and fabricated photonic crystal fibers (PCF). The major merits of these unique light sources are: (1) broad band (covering a wide range of spectroscopic signatures), (2) spatially coherent (so that beams can be delivered to the far distance like laser beams), (3) compact, portable and small footprint (all fiber design), (4) cost effective (traditional approaches such as cascaded laser systems are complicated and expensive for covering broadband).
A confocal microscope can achieve superior contrast when imaging a certain layer in the bulky samples. However, the parallel signal collection feature of the optical system is sacrificed when the sample is scanned pixel by pixel. In this paper, we proposed a novel confocal microscope design that uses a time and spatially multiplexed method, which dramatically increases the time resolution of a confocal microscope. This design has been used to solve a long-standing problem in cardiac research whether or not a small submembranous domain exists with calcium and sodium ion concentrations significantly different from those measured in bulk cytosol. We applied our time and spatially multiplexed confocal microscope to obtain the transient 3-D distribution of calcium ion concentration in rat cardiac myocytes. Our experimental results prove the feasibility of the technique and also demonstrate the huge potential of this design.
In this paper, we present a low grating lobe optical beam steering technique using unequally spaced phased array, in which the required spacings among phase elements are quantitatively analyzed so that the grating lobe can be minimized by the destructive interference from these unequally spaced phase elements. The large grating lobe is one of the major drawbacks of optical phased array technology, which limits the light efficiency and quality of the light beam. Thus, the low grating lobe technique presented in this paper could substantially improve the light efficiency and the quality of light beam, which may play an important role in a variety of applications such as fast speed ladar beam steering, large size high resolution display, and wide bandwidth free space optics communications.
High precision control is highly desirable when using the selective chemical etching technique to fabricate tapered fibers for many practical applications. So far, various methods have been proposed on this topic. In this paper, we proposed a novel and effective method to make tapered fibers in different shapes and sizes based on automatic control of the immersion depth in chemical etching. We adopted the diluted Hydrofluoric acid as etching solution in our
preliminary experiment, and common selective chemical etching scheme was also implemented in our experiment in which the buffered hydrofluoric acid solution is used. We found out in our study that the etching process can be further controlled by controlling the evaporation of the etching solution. Under near-saturation condition, the ammonium fluoride (NH4F) in the etching solution tends to crystallize as the water evaporates. The evaporation of the water and the crystallization of the ammonium fluoride cause the immersion depth of the etched fiber to decrease in certain rate, which leads to different etching time on different parts of the etched fiber. This fact enables the etched fiber to have a very smooth tapered part. By controlling the changing rate of immersion depth and other etching conditions, we can finely control the shape and size of etched fibers.
In this paper, we presented a novel micro-manipulating method, called 'optical combing', that could improve the retina reattachment surgery results. Optical combing adopts the working principle of optical tweezers (i.e., focused Gaussian beam produces a trapping force when it incidents onto a micro-object. The trapping force can pull the micro-object to the central point of focused laser beam. Optical combing is implemented by scanning a focused laser beam on the misaligned micro objects (such as misaligned photoreceptors). In our preliminary experiment, a set of misaligned micro glass rods was re-aligned by applying this optical combing technology, which verified our theory. In the future, this technique will be used to re-align misaligned photoreceptors in real retina.