Date of download: 6/1/2016 Copyright © 2016 SPIE. All rights reserved. (a) Vision of the Brillouin lidar operated from a helicopter. The center ray represents the laser pulses sent into the water column. The two outer rays depict the generated Brillouin scattered light components, whose frequencies are slightly red-shifted and blue-shifted compared to the original laser radiation. (b) Simulated scattering spectrum at an operating wavelength of nm. The Brillouin sidebands have a width ΔνB and are shifted by ±νB with respect to the elastic scattering. The modulation range of the Brillouin maxima for temperatures between 0°C and 40°C is marked in color online. (c) Temperature uncertainty as a function of the salinity uncertainty for various spectral resolutions of the employed detector. The resolutions of 1.6, 4.9, and 8.2 MHz are chosen in order to arrive at temperature accuracies of 0.1°C, 0.3°C, and 0.5°C, respectively. The procedure to derive these curves was adapted from Ref. [3]. Figure Legend: From: Laboratory demonstration of a Brillouin lidar to remotely measure temperature profiles of the ocean Opt. Eng. 2014;53(5): doi: /1.OE

Date of download: 6/1/2016 Copyright © 2016 SPIE. All rights reserved. Overview of the Brillouin lidar for remotely measuring water temperature profiles. It consists of a frequency-doubled ytterbium-doped fiber amplifier, combined with a rubidium-based detector system. Prior to the edge filter, elastic scattering is eliminated via an absorption filter and the beam is split to account for normalization. The relevant term schemes of ytterbium and rubidium are depicted. Figure Legend: From: Laboratory demonstration of a Brillouin lidar to remotely measure temperature profiles of the ocean Opt. Eng. 2014;53(5): doi: /1.OE

Date of download: 6/1/2016 Copyright © 2016 SPIE. All rights reserved. Experimental setup of the detector system, consisting of the absorption filter and the ESFADOF edge filter. Two separate tapered amplifiers (TAs) are used for optical pumping of the vapors. The upper part shows the water tube system, in which Brillouin scattered light is generated by the pulsed fiber amplifier. Abbreviations: wave plate (λ/2, λ/4), polarizing beam splitter cube (PBS), temperature sensor (Pt100), lens (L), pinhole (P), dichroic mirror (DM), mirror (M), rubidium vapor cell (Rb), tapered amplifier (TA), bandpass filter (BP), photomultiplier tube (PMT). Figure Legend: From: Laboratory demonstration of a Brillouin lidar to remotely measure temperature profiles of the ocean Opt. Eng. 2014;53(5): doi: /1.OE

Date of download: 6/1/2016 Copyright © 2016 SPIE. All rights reserved. Transmission spectra of (a) the absorption filter and (b) the ESFADOF edge filter. The latter is depicted for two different pump powers. The spectral regions where the maxima of Brillouin scattering vary with temperature are marked in gray. Figure Legend: From: Laboratory demonstration of a Brillouin lidar to remotely measure temperature profiles of the ocean Opt. Eng. 2014;53(5): doi: /1.OE

Date of download: 6/1/2016 Copyright © 2016 SPIE. All rights reserved. (a) Simulated transmission of Brillouin scattered light through the ESFADOF edge filter, based on the measured spectra shown in Fig. 4(b). The transmission is normalized to the total intensity of both Brillouin components. The salinity was assumed to be zero. (b) Simulated temperature error as a function of the frequency detuning of the lidar laser source, based on the ESFADOF spectrum at a pump power of 102 mW. Figure Legend: From: Laboratory demonstration of a Brillouin lidar to remotely measure temperature profiles of the ocean Opt. Eng. 2014;53(5): doi: /1.OE

Date of download: 6/1/2016 Copyright © 2016 SPIE. All rights reserved. Spatially resolved Brillouin backscatter intensity from the water tubes at room temperature, recorded by PMT1. One thousand successive shots (colored in online) and their average (white dots) are shown. The spatial extent of the water volumes are marked in gray. Figure Legend: From: Laboratory demonstration of a Brillouin lidar to remotely measure temperature profiles of the ocean Opt. Eng. 2014;53(5): doi: /1.OE

Date of download: 6/1/2016 Copyright © 2016 SPIE. All rights reserved. Calibration procedure of the ESFADOF edge filter. (a) Applied temperature curves measured by Pt100 sensors within the tubes. (b) Normalized transmission averaged over the tube’s spatial extents extracted from the data shown in (c). (c) and (d) Normalized edge filter transmission within the calibration and the measurement phase, respectively. The transmission range within the tube’s spatial extents during the calibration phase is marked gray in both graphs. Figure Legend: From: Laboratory demonstration of a Brillouin lidar to remotely measure temperature profiles of the ocean Opt. Eng. 2014;53(5): doi: /1.OE

Date of download: 6/1/2016 Copyright © 2016 SPIE. All rights reserved. Calibration curves relating the mean transmission values within the calibration phase from Fig. 7(b) to the sensor-measured temperatures from Fig. 7(a). Figure Legend: From: Laboratory demonstration of a Brillouin lidar to remotely measure temperature profiles of the ocean Opt. Eng. 2014;53(5): doi: /1.OE

Date of download: 6/1/2016 Copyright © 2016 SPIE. All rights reserved. Spatially resolved temperature determination with the Brillouin lidar, based on the calibration curves shown in Fig. 8. (a) and (b) Temperatures measured by Pt100 sensors as well as by lidar averaging 1000 and 50,000 successive shots, respectively. For the latter, the individual deviations are plotted. (c) Transition from the calibration to the measurement phase in tube 1 at an averaging number of 100,000. (d) Mean temperature deviation regarding both tubes as a function of the averaging number and the acquisition duration, respectively. Figure Legend: From: Laboratory demonstration of a Brillouin lidar to remotely measure temperature profiles of the ocean Opt. Eng. 2014;53(5): doi: /1.OE

Date of download: 6/1/2016 Copyright © 2016 SPIE. All rights reserved. Calculated detection depth as a function of the attenuation coefficient, depicted on a double logarithmic scale, for various averaging numbers. A desired temperature accuracy of 0.5°C, a pulse energy of 1 mJ, and known salinity were assumed. Figure Legend: From: Laboratory demonstration of a Brillouin lidar to remotely measure temperature profiles of the ocean Opt. Eng. 2014;53(5): doi: /1.OE