Free-space optics

Many classical optical sensing principles, which are well known from free space optics can be implemented in integrated optical structures, while integrated optics at its turn can act as source of new principles. Many types of integrated optical sensors have been investigated and demonstrators have been realized, mostly at universities and other research institutes. And also at... 

The levitated laser dye droplet was optically pumped by a pulsed (pulse length 5 ns, repetition rate 10 Hz), frequency-doubled Nd YAG laser (2 = 532 nm) in free-space optical setup. Droplet light emission was collected by a multimode optical fiber placed at an angle of approximately 50° relative to pump laser beam. Collected light was analyzed in a fixed-grating spectrometer with a resolution of FWHM 0.15 nm. 

Teitelbaum M.E., Yarlagadda S., O Brien D., Wetzel E., Goossen K.W. (2008), Normal incidence free space optical data porting to embedded communication links. IEEE Transactions on Components and Packaging Technologies, vol. 31, no. 1, pp. 32-38... 

Level 5 (genius) pixels (thousands of transistors) have complexities, in general, above a thousand active devices, a level of complexity sufficient for implementing application-specific integrated circuits (ASICs) and microprocessors. But this functionality level has problems not faced by the lower levels. First, for free-space optical interconnection, optical I/Os should be arranged in a structured two-dimensional pattern in order to effectively use the two-dimensional nature of imaging optics. On the other hand, computer-aided design (CAD) tools for elec-... 

Mazurczyk et al. [3] fabricated an integrated fluorescence detection system with the microfluidic lab-on-a-chip device. Various arrangements were tested for the fluorescence beam detection like free space optics, fiber optics, and fully waveguiding optics. Eree space optics was found to have the higher sensitivity, but it needed the bulk microscope-based detection system. Eiber and fully waveguiding optics seemed to be the possible option to overcome the bulk microscope setup, but their sensitivity was not found to be sufficient especially for high sensitivity required applications. Anyhow, they showed the feasibility of their device for... 

Work in this area has recently been extended by Terray et al. [5] who have recently integrated this into a microfluidic device format for paflio-gen detection, demonstrating very precise separation between very closely related bacteria Bacillus anthracis and Bacillus thuringiensis and millimeter-scale separation. In their work a loosely focused laser beam propagates in a direction opposite to the fluid flow in the poly (dimethylsiloxane) (PDMS) channel. As a result of the difference in the optical forces on the cells, they come to rest at different points alrnig the length of the channel. At present, however, such systems are practically limited by the fundamentals of the free-space optics on which they rely. 

Free-space optical manipulation techniques in microfluidic systems have recently generated a signiflcant amount of interest. Classically the advantage of these optical approaches lies in their ability to provide remote operation and handle individual particles directly as opposed to indirect manipulation of the stUTounding flow field. The precision with which particles can be transported and separated with these optical techniques makes them particularly useful for biomedical analysis devices. While extremely flexible and relatively easy to implement (see the section on Optofluidics Applications and Optofluidics Techniques for Fabrication and Integration), these systems are ultimately limited... 

B. Principle of Polarization-Dependent (Free Space) Optical Isolators... 

Free space optical interconnection networks are preferable over other methods, especially for cases of relatively high interconnection volumes. Free space systems make full use of parallelism since all three spatial dimensions are involved. Flowever, dynamic systems are necessary for telecommunication applications, especially for optical fiber communications. 

On Application of Nonequilibrium Detectors LWIR Free-Space Optics... 

Contemporary infrared (IR) systems for the free-space optics (FSO) in the wireless last-mile access, private networks and mobile infrastructure applications mostly utilize the transmission window 0.7-1.55 pm which is very sensitive to some influences of atmosphere. Rain, fog, smoke, dust particles effectively shorten the available range in this window. Typical fog drops have dimensions comparable to the operating wavelengths, and the resulting real-Ufe maximum distances are typically below 200-300 m, although distances of a few kilometers have been achieved in favorable conditions in point-to-point systems [407]. 

D.P. Hutchinsoit R.K. Richards, All-weather long-wavelength infrared free space optical communications. J. Opt Fibta- Comm. Res. 4(3), 214-224 (2007)... 

Z. JakSic, Z. Djuric, Extraction Photodiodes with Auger Suppression for All-Weather Free-Space Optical CommunicatioiL Electronics 8(1), 30-32 (2004)... 

Usually, a large field of use for MWIR and LWIR detectors is overlooked— the free-space optical (FSO) telecommunicafions. This is certainly unusual when one bears in mind that communications themselves are one of the pillars of civilization itself, actually one could maintain that communications were those that created civilization in the first place. 

Optical interconnections are also starting to be important for solving connectivity problems in large electronic systems [36]. Such interconnections may use free space optics rather than guided wave, and the interconnection patterns may be reconfigur-able [37, 38]. Liquid crystal devices may have a role here [39]. 

Damman grating to replicate the source inputs. The use of the CGH to replicate the inputs comes from the CGH property that the spots in the replay field are the Fourier transform of input illumination. Since only one channel is likely to be required at each output, those not required can be blocked using liquid crystal shutters. Such switches are based on the Stanford vector matrix multiplier (SVMM) [50] related switching devices [51]. When implemented using a CGH to fan out, and with a 2D array of inputs (rather than the 1D arrays of the SVMM) to simplify the free space optics, these are called matrix - matrix switches [52]. This kind of structure is found in a range of optical processing architectures (see Sec. 2.4). For a symmetrical switch with n inputs and n outputs, an array of nxn shutters is required. 

In these equations Ko = 27t/Xo, where Xo is the free-space optical wavelength. It is convenient to make again the identification of li/Ko = c/u = N, the effective refractive index of the guided modes. 

Development, test and evaluation of MEMS micro-mirrors for free-space optical communications, Proc. SPIE 5550, pp. 299-312 (2004). 

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