We report on the design, measurement capabilities, and measured performance of a new Small All-range Lidar (SALI). The lidar transmitter uses a 1.55-μm Erbium-Doped Fiber-Amplifier (EDFA) laser modulated with a return-to-zero pseudo-noise (RZPN) code. The receiver uses a 2x8-pixel HgCdTe avalanche photodiode (APD) array in linear single photon detection mode of operation. The receiver electronics calculate the target range by correlating the received signal with a patented 3-state RZPN kernel. A field programmable gate array (FPGA) processes the signal in real time up to a 120 Hz measurement rate for eight parallel receiver channels. The output power of the fiber laser, the detector gain, and the receiver integration time are all adjustable so that it can measure planetary surface at range from more than 100 kilometers down to a fraction of a meter without saturation. SALI is primarily designed for mapping planetary bodies from orbit but can also be used as a guidance sensor for sample collection or landing. The instrument uses all standard components from the fiber optic communications industry except for the detector and it can be built at a much lower cost compared to previous planetary lidars. SALI is also modular and can use different lasers and detectors at different wavelengths and different receiver telescope sizes to best fit the specific mission requirements. We have recently completed the instrument integration and performed function and performance testing. The measured performance is close to the prediction given in our earlier publications. We will soon conduct a vibration and thermal-vacuum tests to demonstrate its readiness for use in a space mission.
We describe Fibertek’s progress toward commercializing space laser communications and new features of our secondgeneration compact laser communication terminal (LCT). The LCT design is modular, flexible and can accommodate a variety of waveforms and data formats. Fibertek has a unit deployed in space for initial testing followed by additional units for more broad-based market applications. Our first-generation optical telescope assembly was originally designed for NASA Deep Space CubeSat laser communications. It was customized as a complete commercial LEO LCT system which is 2U in size, 2 kg in mass, and provides Gbps data rates. The optical transceiver has a shared transmit/receive optical path that uses a laser beacon to ensure high pointing accuracy, active control of the pointing stability, and ensures a strong optical signal-to-noise ratio (SNR) during link operation. The terminal has been manufactured and tested, providing high accuracy pointing and low jitter. Our second generation LCT system features bidirectional operation and support for an eyesafe beacon for uplink applications. Bi-directional operation is attractive for inter-satellite links (ISL), uplinks of data, pointing acquisition and tracking (PAT), position, navigation and timing (PNT), and for telemetry, tracking, and command (TTandC). The eyesafe uplink beacon makes it easier to get FCC authorization for operation. The LCT includes a 64 mm telescope and a 1.5-μm fiber-amplifier with >2 W optical power that enables future updates to allow operation up to GEO orbit with the addition of SCPPM and 10-100 Gbit/sec.
We report on the development, testing, and initial space qualification of a 1.5-μm, high-power (6 W), high wall-plug efficiency (∼15%), pulse-position-modulated (PPM), polarization-maintaining, fiber laser transmitter subsystem for deep-space laser communication links. Programmable high-order PPM modulation up to PPM-128 formats, with discrete pulse slots ranging from 0.5 to 8 ns, satisfies variety of link requirements for deep-space laser communication to Mars, asteroids, and other deep-space relay links, as per the National Aeronautics and Space Administration’s space laser communication roadmap. We also present initial space qualification results from thermal-vacuum tests, vibration testing, radiation testing, and an overall reliability assessment.
We report on the development, testing and initial space qualification of a 1.5-μm, high-power (6W), high wall-plug efficiency (~15%), pulse-position-modulated (PPM), polarization-maintaining (PM), fiber laser transmitter subsystem for deep-space laser communication links. Programmable high-order PPM modulation up to PPM-128 formats, with discrete pulse slots ranging from 0.5- to 8-nsec, satisfies variety of link requirements for deep space laser communication to Mars, asteroids, and other deep-space relay links, per NASA's space laser communication roadmap. We also present initial space qualification results from thermal-vacuum tests, vibration testing, radiation testing and overall reliability assessment.
Fibertek has developed a space qualifiable, highly efficient, high power (<5W), fiber based 1.5um laser optical module (LOM). The transmitter achieves 6W average and <1kW peak power out of a 2m long single mode delivery fiber with 8nsec pulses and <6Ghz linewidth. Stimulated Brillouin Scattering (SBS) is managed by precise linewidth control and by use of LMA gain fiber in the power stage while maintaining the required diffraction limited, and highly polarized (PER<20dB) output. Size and weight of the built LOM are 8”x10”x2.375” and 3 kg, respectively. With improvements in the modulation scheme and component specification, achieved LOM electrical to optical efficiency is over 17.0%. Highly efficient operation is sustained for a wide range of pulse-position modulation (16 to 128-ary PPM) formats with pulse widths varying from 8nsec to 0.5nsec and operation temperature 10-50C. Pressure stress analysis, random vibration analysis and thermal analysis of the designed LOM predicts compliance with NASA GEVS levels for vibration and thermal cycling in a vacuum environment. System will undergo both thermal vacuum and vibration testing to validate the design.
Space based laser remote-sensing for Earth observation and planetary atmospheres has traditionally relied on the mature diode-pumped solid-state laser and nonlinear frequency conversion technology. We highlight representative examples, including ongoing space mission programs at Fibertek. Key design issues are highlighted, and the lessons learned from a multi-disciplinary design process addressing the space-qualification requirements. Fiber laser/amplifier system provides an agile optical platform for space based laser applications ‒ space lasercom, space-based Earth (or planetary) remote sensing, and space-based imaging. In particular we discuss ongoing efforts at Fibertek on a space-qualifiable, high-performance 1.5-μm Er-doped fiber laser transmitter for inter-planetary lasercom. Design and performance for space qualification is emphasized. As an example of an agile laser platform, use of above fiber laser/amplifier hardware platform for space based sensing of atmospheric CO2 is also highlighted.
Heavy metal oxide glasses exhibiting high transmission in the Mid-Wave Infra-Red (MWIR) spectrum are often difficult to manufacture in large sizes with optimized physical and optical properties. In this work, we researched and developed improved tellurium-zinc-barium and lead-bismuth-gallium heavy metal oxide glasses for use in the manufacture of fiber optics, optical components and laser gain materials. Two glass families were investigated, one based upon tellurium and another based on lead-bismuth. Glass compositions were optimized for stability and high transmission in the MWIR. Targeted glass specifications included low hydroxyl concentration, extended MWIR transmission window, and high resistance against devitrification upon heating. Work included the processing of high purity raw materials, melting under controlled dry Redox balanced atmosphere, finning, casting and annealing. Batch melts as large as 4 kilograms were sprue cast into aluminum and stainless steel molds or temperature controlled bronze tube with mechanical bait. Small (100g) test melts were typically processed in-situ in a 5%Au°/95%Pt° crucible. Our group manufactured and evaluated over 100 different experimental heavy metal glass compositions during a two year period. A wide range of glass melting, fining, casting techniques and experimental protocols were employed. MWIR glass applications include remote sensing, directional infrared counter measures, detection of explosives and chemical warfare agents, laser detection tracking and ranging, range gated imaging and spectroscopy. Enhanced long range mid-infrared sensor performance is optimized when operating in the atmospheric windows from ~ 2.0 to 2.4μm, ~ 3.5 to 4.3μm and ~ 4.5 to 5.0μm.
Various military lidar applications such as underwater mine detection, obstacle avoidance, IRCM, and 3 D lidar incorporate high repetition rate solid-state lasers to accomplish the mission. The recent advances and demonstrations in high power Ytterbium (Yb) fiber lasers/amplifiers make the fiber media a viable alternative to bulk lasers for these applications. The fiber laser geometry maximizes the pump absorption and mode matching for overall high efficiency, (factor-of-two over bulk laser sources) while minimizing thermal effects. In this presentation we will show experimental and modeling results on various master oscillator Yb doped polarization maintaining (PM) fiber amplifiers being developed for high repetition rate applications. We have demonstrated >20 W of average output power with M2 <1.3, repetition rates up to 75 kHz and pulse widths ranging from <1 ns to 250 ns. Results of a pulsed PM MOFA efficiently pumping a Periodically Poled Lithium Niobate (PPLN) optical parametric oscillator (OPO) and KTP doubler will also be presented.
Pyrromethene-BF2 (PM) complexes doped in modified polymethyl methacrylate were evaluated and show excellent laser efficiency and damage resistance when excited at 532 nm. The spectroscopy and laser performance of a new laser dye (PM511) is discussed with emission below 550 nm. In addition, the enhanced sensitization and dual wavelength operation of dyes doped in the solid-state are demonstrated between 550 - 650 nm.
A 6.3 mm diameter by 15 mm long a-axis Nd:YLiF4 (YLF) laser rod was side-pumped by a 475 W GaAlAs diode array. A 42.9 percent optical slope efficiency was achieved while pumping in a region of low absorption in the 2H9/2, 4F5/2 band at 806 nm. Findlay-clay loss analysis and pump absorption profiles are discussed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.