Room temperature terahertz wave imaging at 60 fps by frequency up-conversion in DAST crystal

Terahertz imaging has attracted a lot of interests for more than 10 years. But real time, high sensitive, low cost THz imaging in room temperature, which is widely needed by fields such as biology, biomedicine and homeland security, has not been fully developed yet. A lot of approaches have been reported on electro-optic (E-O) imaging and THz focal plane arrays with photoconductive antenna or micro-bolometer integrated. In this paper, we report high sensitive realtime THz image at 60 frames per second (fps) employing a commercial infrared camera, using nonlinear optical frequency up-conversion technology. In this system, a flash-lamp pumped nanosecond pulse green laser is used to pump two optical parametric oscillator systems with potassium titanyl phosphate crystals (KTP-OPO). One system with dual KTP crystals is used to generate infrared laser for the pumping of THz difference frequency generation (DFG) in a 4- Dimethylamino-N-Methyl-4-Stilbazolium Tosylate (DAST) crystal. The other one is for generation of pumping laser for THz frequency up-conversion in a second DAST crystal. The THz frequency can be tuned continuously from a few THz to less than 30 THz by controlling the angle of KTP crystals. The frequency up-converted image in infrared region is recorded by a commercial infrared camera working at 60 Hz. Images and videos are presented to show the feasibility of this technique and the real-time ability. Comparison with a general micro-bolometer THz camera shows the high sensitivity of this technique.

[1]  Roberto Morandotti,et al.  CCD-based imaging and 3D space-time mapping of terahertz fields via Kerr frequency conversion. , 2013, Optics letters.

[2]  Hiromasa Ito,et al.  High-sensitivity detection of terahertz waves using nonlinear up-conversion in an organic 4-dimethylamino-N-methyl-4-stilbazolium tosylate crystal , 2010 .

[3]  Naoki Oda,et al.  Uncooled bolometer-type Terahertz focal plane array and camera for real-time imaging , 2010 .

[4]  Joo-Hiuk Son,et al.  Measurement depth enhancement in terahertz imaging of biological tissues. , 2013, Optics express.

[5]  Nikolai A. Maleev,et al.  High-responsivity terahertz detection by on-chip InGaAs/GaAs field-effect-transistor array , 2011 .

[6]  M. Koch,et al.  Terahertz imaging: a new non-destructive technique for the quality control of plastic weld joints , 2007 .

[7]  Yuma Takida,et al.  10 aJ-level sensing of nanosecond pulse below 10 THz by frequency upconversion detection via DAST crystal: more than a 4 K bolometer. , 2014, Optics letters.

[8]  Wei Shi,et al.  Observation of THz to near-Infrared parametric conversion in ZnGeP(2) crystal. , 2006, Optics express.

[9]  Xiang Zhang,et al.  Two‐dimensional electro‐optic imaging of THz beams , 1996 .

[10]  Hiromasa Ito,et al.  Frequency-agile THz-wave generation and detection system using nonlinear frequency conversion at room temperature. , 2010, Optics express.

[11]  K. Sertel,et al.  A Broadband Focal Plane Array Camera for Real-time THz Imaging Applications , 2013, IEEE Transactions on Antennas and Propagation.

[12]  Derek Abbott,et al.  Analysis of system trade-offs for terahertz imaging , 2000 .

[13]  Sumanth Kaushik,et al.  Ultrasensitive, Room Temperature Detection of THz Radiation Using Nonlinear Parametric Conversion , 2011, IEEE Journal of Selected Topics in Quantum Electronics.

[14]  J. Federici,et al.  THz imaging and sensing for security applications—explosives, weapons and drugs , 2005 .

[15]  Hans-Georg Meyer,et al.  Uncooled antenna-coupled terahertz detectors with 22 μs response time based on BiSb/Sb thermocouples , 2013 .

[16]  Kodo Kawase,et al.  Terahertz Imaging System for Medical Applications and Related High Efficiency Terahertz Devices , 2014 .

[17]  Kyung Hyun Park,et al.  InGaAs Schottky barrier diode array detector for a real-time compact terahertz line scanner. , 2013, Optics express.

[18]  Kun Huang,et al.  Ultrasensitive mid-infrared up-conversion imaging at few-photon level , 2013 .

[19]  Viktor Krozer,et al.  CMOS detector arrays in a virtual 10-kilopixel camera for coherent terahertz real-time imaging. , 2012, Optics letters.

[20]  A. Yasuda,et al.  Terahertz imaging applied to cancer diagnosis , 2010, Physics in medicine and biology.

[21]  T. Yasui,et al.  Terahertz paintmeter for noncontact monitoring of thickness and drying progress in paint film. , 2005, Applied optics.

[22]  Jeppe Seidelin Dam,et al.  Room-temperature mid-infrared single-photon spectral imaging , 2012, Nature Photonics.

[23]  Ryoichi Fukasawa,et al.  Terahertz imaging of silicon wafers , 2002 .

[24]  Patrick Mounaix,et al.  Non-invasive investigation of art paintings by terahertz imaging , 2010 .

[25]  A. Minamide,et al.  Ultra-wideband THz detection by using DAST crystal based on frequency up-conversion technique , 2012, 2012 37th International Conference on Infrared, Millimeter, and Terahertz Waves.

[26]  Kodo Kawase,et al.  Terahertz Imaging For Drug Detection And Large-Scale Integrated Circuit Inspection , 2004 .

[27]  Jingzhou Xu,et al.  Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging , 2005 .

[28]  Thomas Rades,et al.  Evaluating the effect of coating equipment on tablet film quality using terahertz pulsed imaging. , 2013, European journal of pharmaceutics and biopharmaceutics : official journal of Arbeitsgemeinschaft fur Pharmazeutische Verfahrenstechnik e.V.

[29]  J. C. Macfarlane,et al.  Towards large scale HTS Josephson detector arrays for THz imaging , 2013 .