USA As Represented by Secretary of the Navy

Other

Veerendra Kumar Mathur

John H Barkyoumb

Noel A Guardala

Ross S Fontenot

Zameer Ul Hasan

Kishalaya Chakrabarti

Stephen A Mastro

Jack L Price

Andrew W Jarrett

Johnathan D Wensman

According to exemplary practice of the present invention, a probe laser beam characterized by a Stokes luminescence wavelength is trained upon a thermally insulated medium; the Stokes luminescence is measured upon conclusion of the probe laser impingement of the medium. Following this first Stokes luminescence measurement, a pump laser beam characterized by an anti-Stokes luminescence wavelength is trained upon the medium; the Stokes luminescence is measured upon conclusion of the pump laser impingement of the medium. Each laser has a blocking device associated therewith. A computer is implemented to transmit control signals to open and close the two blocking devices in alternating fashion so that only one laser beam at a time is aimed at the medium. The computer is also implemented to process the measurement signals to determine heating versus cooling. If the luminescence intensity following the pump laser impingement exceeds the luminescence intensity following the probe laser impingement, then the medium is being cooled.

Automated noncontact method to discriminate whether cooling or heating is occurring

According to exemplary practice of the present invention, a probe laser beam is aligned with a position detector and is spatially/geometrically related to a pump laser beam. A temperature gradient is produced in a medium by the pump beam. Since an increase or decrease in the temperature of the medium is related to an increase or decrease in the refractive index of the medium, position sensing of the deflection of the probe beam relative to the pump beam indicates whether the medium is heating or cooling.

Photothermal deflection spectroscopy method for heating-cooling discrimination

An inventive neutron detector includes an n-type GaN wafer and a photomultiplier, which are optically coupled with each other. The n-type GaN wafer is irradiated with neutrons from a neutron source, such as including a particle accelerator and a beryllium target. Scintillation of the n-type GaN resulting from the neutron irradiation is amplified by the photomultiplier and is analyzed using a data acquisition system.

N-type gallium nitride scintillation for fast-neutron detection

Typical practice of the present invention performs measurement and processing of two forms of light emissions&#x2014;viz., unfiltered and filtered&#x2014;of a core-valence luminescent (CVL) scintillator impinged by ionizing radiation emanating from a radioactive source. When unfiltered, the CVL scintillator light emission is inclusive of gamma emissions and neutron emissions. When filtered by a filtering apparatus that transmits CVL light only, the CVL scintillator light emission is inclusive of gamma emissions but is exclusive of neutron emissions. Algorithmic comparison between the two sets of empirical data provides discriminative information regarding gamma emissions versus neutron emissions. Essentially, the difference is taken between the unfiltered pulse height spectra data and the filtered pulse height data. The set of pulse height spectral data thus computed via subtraction is indicative of the portion of the CVL scintillator light emissions that is inclusive of neutron emissions but is exclusive of gamma emissions.

Spectrally resolved pulse height analysis for neutron-gamma discrimination

A color switchable stress/fracture sensor in combination with a structure. The combination apparatus includes a structure requiring stress and/or fracture detection, and at least one elasto-mechanoluminescent material at least partially dispersed in and/or on the structure and/or in a coating on the structure. The combination apparatus further includes at least one fracto-mechanoluminescent material at least partially dispersed in and/or on the structure and/or in a coating on the structure, and at least one fiber optic cable positioned to receive and transmit sufficient light emitted from the elasto-mechanoluminescent material due to stress applied to the elasto-mechanoluminescent material and to receive and transmit sufficient light emitted from the fracto-mechanoluminescent material due to fracture of the fracto-mechanoluminescent material.

Color switchable stress-fracture sensor for damage control

A composite structure contains crystalline and/or polycrystalline triboluminescent elements distributed therein externally and/or internally, totally and/or regionally. The structure is instrumented with at least one optical fiber which is coupled therewith penetratingly and/or superficially/tangentially. Each optical fiber is exteriorly light transparent/translucent along at least a longitudinal portion thereof which is situate in the vicinity of at least one triboluminescent element. Concomitant with the occurrence of damage in and/or on the structure is the occurrence of mechanical action with respect to at least one triboluminescent element, a consequence of which is the occurrence of triboluminescence which, to at least some degree, passes radially into at least one optical fiber so as to reach the optical fiber's transmissive axial core and thereby be transmitted to remotely located photosensitive equipment. The triboluminescent elements can exist wholely and/or partly in various capacities, e.g., as fiber reinforcement and/or particle reinforcement and/or particle filler.

Fiber optic composite damage sensor

High density, photon-gated persistent spectral holeburning is effectuated in rare earth doped II-VI compounds such as MgS, CaS, BaS and SrS. Two-photon ionization of rare earth ions is performed, selected by a narrow band laser, producing narrow regions of reduced absorption (optical holes) in the absorption spectrum of a rare earth ion. These holes are useful for such applications as high density memory (especially, high density re-writable or photo-erasable memory), spectral holographic memory, communication, etc., no and demonstrate great survivability over reading cycles, thermal cycles and elevated temperatures. The embedment of the rare earth doped II-VI compound in a matrix comprising a polymeric material (such as PMMA), prior to the effectuation of the holeburning, may be advantageous for many embodiments. Inventive practice has successfully burned two hundred forty photon gated spectral holes in the zero phonon line (ZPL) of the 4f-5d transition of Eu in a magnesium sulfide host. CaS:Eu, CaS:Eu,Sm and MgS:Eu are among the materials which have demonstrated a very high density of spectral holes.

II-VI compounds as a medium for optical data storage through fast persistent high density spectral holeburning

High density, photon-gated persistent spectral holeburning is effectuated in rare earth doped II-VI compounds such as MgS, CaS, BaS and SrS. Two-photon ionization of rare earth ions is performed, selected by a narrow band laser, producing narrow regions of reduced absorption (optical holes) in the absorption spectrum of a rare earth ion. These holes are useful for such applications as high density memory (especially, high density re-writable or photo-erasable memory), spectral holographic memory, communication, etc., and demonstrate great survivability over reading cycles, thermal cycles and elevated temperatures. The embedment of the rare earth doped II-VI compound in a matrix comprising a polymeric material (such as PMMA), prior to the effectuation of the holeburning, may be advantageous for many embodiments. Inventive practice has successfully burned two hundred forty photon gated spectral holes in the zero phonon line (ZPL) of the 4  transition of Eu in a magnesium sulfide host. CaS:Eu, CaS:Eu,Sm and MgS:Eu are among the materials which have demonstrated a very high density of spectral holes.

High density and fast persistent spectral holeburning in II-VI compounds for optical data storage

Spectral shift between different wavelength spectra by restricted narrow bandgap absorption of incident radiation at one location on a semiconductor body, under electrical bias causing release of radiation at another emission location as a result of radiative electron-hole recombination. The semiconductor body is a graded bandgap establishing composition of two selected compounds alloyed to a variable, position-dependent degree between the respective radiation and emission locations at which the respective narrow and wide bandgap properties of the compounds prevail.

Graded bandgap semiconductor device for real-time imaging

Magnesium oxide sensing material is pretreated and charged by UV radiation o identify impingement thereon of radiation from a near infrared laser source by detection of blue emissions which persist for an unusually long period of time, avoiding frequent respotting and recharging. When heated to thermoluminescence peaks above room temperature by irradiation from a far infrared laser source, the magnesium oxide exhibits green luminescence enabling wavelength discrimination between detection of near and far infrared laser sources. Such pretreated magnesium oxide also produces green emissions when irradiated by UV laser sources, to distinguish between detection of the UV laser sources and the far infrared laser sources by discrimination between different fading behaviors of the green emissions.

Laser detection and discrimination system

A method of determining the nature of an unspecified laser source using the optically and thermally stimulated luminescence characteristics of a single MgS phosphor doped with either Ce, Sm or Eu, Sm ions. The doped MgS phosphor is first exposed to charging radiation thereby allowing electron trapping to occur. Subsequent to the electron trapping, the phosphor is exposed to the energy of an unspecified laser source which frees the trapped electrons. The freed electrons are then available for recombination which results in a specific color luminescence indicative of the type of laser source.

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Beltsville, MD, United States of America

Veerendra Kumar Mathur