Quantum Imaging Technologies: Quantum Laser Radar

Transcription

1 MURI 2005 Quantum Imaging: New Methods and Applications Year 3 Review / 17 November 2008 / UMBC, Baltimore, MD Quantum Imaging Technologies: Quantum Laser Radar Prem Kumar and Geraldo Barbosa EECS Department, Northwestern University, Evanston, IL s: kumarp@northwestern.edu; g-barbosa@northwestern.edu Jeffrey Shapiro Research Laboratory of Electronics, MIT, Cambridge, MA jhs@mit.edu Support: U. S. Army Research Office Multidisciplinary University Research Initiative Grant No W911NF Quantum Imaging Review, UMBC, Slide # 1

2 Quantum Laser Radar Classical or Quantum Target Glint / Speckle Transmitter Receiver Optical Pre-processing Optical Post-processing Transmit Optics Receive Optics Atmospheric Turbulence Direct Heterodyne Homodyne PIA PSA χ (2) χ (3) Quantum return severely degraded by loss keep quantum local PIA = Phase Insensitive Amplifier PSA = Phase Sensitive Amplifier Quantum Imaging Review, UMBC, Slide # 2

3 Pictorial View of Amplification of Coherent Input Light E = X + i Y Y Phasesensitive Phaseinsensitive Y σ out2 = (2G -1) σ in 2 X X Y σ X2 = g σ in 2 σ Y2 = g -1 σ in 2 t E = X cosω t -Ysinω t X Quantum Imaging Review, UMBC, Slide # 3

4 Simulation of Preamplified Photodetection of Shot-Noise Limited Signals Simulation of the amplification of a gray-scale image in the shot-noise limited regime Random zero-mean Gaussian noise is added to represent detector noise A valid model when the received signal photon number per pulse or per inverse bandwidth is large Photocurrents in the unamplified and amplified cases are scaled appropriately for fair comparison. Quantum Imaging Review, UMBC, Slide # 4

5 Simulation of Preamplified Photodetection of Shot-Noise Limited Signals For G = 1 (no preamplification) SNR IN = N s (shot-noise limited signal) N s Efficiency 0 < η 1 η Ideal Detector (ΔN s ) 2 η = ηn s, SNR OUT = ηn s NF = SNR IN / SNR OUT = 1/η For G > 1 SNR IN = N s and (ΔN s ) 2 = N s N s G η Output = ηgn s. Find (ΔN s ) 2 ηg from: NF = SNR IN / SNR OUT = N s / [(ηgn s ) 2 / (ΔN s ) 2 ηg ] or (ΔN s ) 2 ηg = NF (ηgn s ) 2 / N s = (ΔN s ) 2 η ηg 2 NF Quantum Imaging Review, UMBC, Slide # 5

6 Simulation of Preamplified Photodetection of Shot-Noise Limited Signals Noise Figure (NF): [PRL 83 (10), pp , Choi, Vasilyev & Kumar] NF tot = NF amp + (1 - η) / (ηg) NF PSA = 1 (NF PSA ) tot = 1 + (1 - η) / (ηg) NF PIA = 2 1/G (NF PIA ) tot = 2 (1 1/G) + 1 / (ηg) Also, the detected signal in each case is different. So, we scale PSA & PIA noise by G 2 in order to fairly compare the photo-current between the three cases. Therefore, added noise: No gain (ΔN s ) 2 η PSA η [1 + (1 - η) / (ηg)] (ΔN s ) 2 η PIA η [2(1 1/G) + 1/(ηG)] (ΔN s ) 2 η Quantum Imaging Review, UMBC, Slide # 6

7 Simulation of Potential Advantage Although shown here for a spatially broadband case, our goal in the MURI is to do proof-of-principle experiments with raster scanning of the image with use of a fiber-based PSA. Soft Gaussian Frequency Filter FFT + Start w/ image Add noise per spatial frequency: (ΔN s ) 2 η When G = 1 IFFT η [1 + (1 η)/(ηg)] (ΔN s ) 2 η For PSA η [ 2(1 1/G) + 1/(ηG)] (ΔN s ) 2 η For PIA Result Quantum Imaging Review, UMBC, Slide # 7

8 Results: Averaged over 100 Frames η = 0.8, G = 10 db Target (no average) No gain PSA gain PIA gain One frame after IFFT (no average) Quantum Imaging Review, UMBC, Slide # 8

9 Results: Averaged over 100 Frames η = 0.3, G = 10 db Target (no average) No gain PSA gain PIA gain One frame after IFFT (no average) Quantum Imaging Review, UMBC, Slide # 9

10 Our PSA Experimental Setup 75MHz Σ ~ 15GHz 40MHz ~ ~ X EDFA PM IM nm 3-stage FBG PZT High Power EDFA 90:10 Signal Detection 99:1 Pump isolation 99:1 99:1 HNLF FM Gain Monitor for PLL Ref. Output of PSA Ref. Input of PSA Quantum Imaging Review, UMBC, Slide # 10

11 Key Steps in the Measurement Scheme Optical Signal preparation pump signal idler 40MHz 30GHz Employs phase locking loop with piezoelectric transducer for phase-sensitive amplification Double pass Highly Nonlinear Fiber Noise measurement on the analog signal Quantum Imaging Review, UMBC, Slide # 11

12 Direct Signal and Noise Measurements Pump Isolation PSA 50/50 EXT-75 Detector +/- ESA 60dB Amp. BPF (35-45MHz) Quantum Imaging Review, UMBC, Slide # 12

13 Noise Figure Measurement of the Fiber PSA Lim, Grigoryan, Shin, & Kumar, OFC 2008 NF ave (Anti-Stokes) = (0.42 ± 0.53) db NF ave (Stokes) = (0.68 ± 0.59) db Quantum Imaging Review, UMBC, Slide # 13

14 Proposed Proof-of-Principle Experiment Quantum Imaging Review, UMBC, Slide # 14

15 Experiment in Progress Source laser (CW nm) modulated signal EDFA Pre- Amplifier Transmitter Signal Generation 30GHz Double sideband modulation Phase modulation SBS suppression Phase-lock loop Phase-delay generator PSA Based Receiver Feed back HNLF with Faraday mirror terminal Optical signal Electrical signal Three-stage FBG sideband separator Circulator Test pattern Free space testbed EDFA PSA Output Quantum Imaging Review, UMBC, Slide # 15