A new scheme for distributed Brillouin sensing of strain and temperature in optical fibers is proposed, analyzed and demonstrated experimentally. The technique combines between time-domain and correlation-domain analysis. Both Brillouin pump and signal waves are repeatedly co-modulated by a relatively short, high-rate phase sequence, which introduces Brillouin interactions in a large number of discrete correlation peaks. In addition, the pump wave is also modulated by a single amplitude pulse, which leads to a temporal separation between the generation of different peaks. The Brillouin amplification of the signal wave at individual peak locations is resolved in the time domain. The technique provides the high spatial resolution and long range of unambiguous measurement offered by correlation-domain Brillouin analysis, together with reduced acquisition time through the simultaneous interrogation of a large number of resolution points. In addition, perfect Golomb codes are used in the phase modulation of the two waves instead of random sequences, in order to reduce noise due to residual, off-peak Brillouin interactions. The principle of the method is supported by extensive numerical simulations. Using the proposed scheme, the Brillouin gain spectrum is mapped experimentally along a 400 m-long fiber under test with a spatial resolution of 2 cm, or 20,000 resolution points, with only 127 scans per choice of frequency offset between pump and signal. Compared with corresponding phase-coded, Brillouin correlation domain analysis schemes with equal range and resolution, the acquisition time is reduced by a factor of over 150. A 5 cm-long hot spot, located towards the output end of the pump wave, is properly identified in the measurements. The method represents a significant advance towards practical high-resolution and long range Brillouin sensing systems.

Passive Q switching of a Tm:YAP solid-state laser at 1935 nm with Cr:ZnSe and Cr:ZnS polycrystalline saturable absorbers is demonstrated for the first time, to the best of our knowledge. With Cr:ZnS, a maximum pulse energy of 1.85 mJ is obtained for a pulse duration of 35.8 ns, resulting in a peak power of 51.7 kW. With Cr:ZnSe, the achieved pulse energy of 1.55 mJ with a pulse duration of 42.2 ns leads to 36.7-kW peak power. These high pulse energies, together with the unique lasing wavelength at 1935 nm, make this laser a promising tool for biomedical and microsurgery applications.

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Modern electro-optical systems contain several components such as thermal imager, laser designator, laser range finder, etc. The dem and for com pact syste ms w ith l ow po wer co nsumption an d l ow cost can be ad dressed by i ncorporating some of the traditional system abilities into the IR detector. We present SNIR, a new type of detector, which consists of a Read O ut Int egrated C ircuit (R OIC) wi th adva nced o n-chip si gnal p rocessing. T he R OIC i s fl ip chi p-bonded to a 640×512 In Sb det ector ar ray of 1 5µm pi tch. S NIR di gital R OIC can b e ope rated i n either o ne of t he f ollowing f our different modes of operation. The first operation mode is standard thermal imaging, which has typical functionalities and performance of MWIR detector. The second operation mode is a dual-function mode that includes both standard thermal imaging and information on Asynchronous Laser Pulse Detection (ALPD) for each pixel. The detection probability of a laser pu lse is significantly in creased by i ntegrating a dedicated i n-pixel circu it fo r iden tifying a fast sig nal tem poral profile. Since each pixel has internal processing to ide ntify laser pulses, it is possible a lso to m easure the ela psed time between a trigg er and th e detection of a laser pulse. Th is yi elds a t hird m ode of operation i n which the detector i s synchronized t o a l aser an d becomes a Tw o-dimensional Laser R ange Finder (TLRF). T he forth operation m ode i s dedicated to Low Noise Imaging (LNIM) for the SWIR band, where the IR radiation signal is low. It can be used in both passive or active imaging. We review some of t he predicted and measured results for the different modes of operation, both at the detector level and at the system level.

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