PPM laser transmitters, particularly with ultra-low electrical power consumption and arbitrary data format, are of significant interest for many NASA programs. The direct NASA application is a PPM laser transmitter with the following characteristics: 10-100-MHz symbol data rate; 250-ps symbol slot width, 16-128 PPM M-ary, 1540-1560 nm wavelength, 50mW average power, 25-ps pulse width, and total average power consumption ≤ 500 mW. Further, the PPM transmitter developed in this program could be directly applied to small systems in near-earth orbit, such as Cubesats, and in proximity-length applications, such as orbiter-to-lander communications. They can also be used to seed a high-power fiber amplifier for interplanetary and deep-space optical communications systems. The transmitter can also be used as the seed for LIDAR transmitters. In conjunction with a low-jitter clock generator, the PPM pulses can be applied to mm-scale ranging for use in identifying objects and mapping contoured structures. The technology in our commercial CavitylessTM pulse source results in ultra-low-loss optical pulse generation with less than 25-fs jitter, and an optical engine that adds less than 5-fs of additive jitter.
The clear first application is as a seed for long-range, high-performance LIDAR laser systems. One specific LIDAR application is differential absorption LIDAR, which require laser sources operating at 1.57μm for sensing CO2. The technology developed in this program, although focusing on 1.5μm for the particular communication application, is not specifically dependent on the wavelength of the light. By using alternate laser diodes and fiber amplifiers (doped with Yb, Tm, or Ho instead of Er), the 1-μm window can be reached as well as the 2.05-μm CO2 line, which is immediately applicable to environmental and pollution monitoring. A multitude of other photon-starved applications require format-flexible PPM transmitters, such as deep-sea sensing, aircraft-to-submarine communications, secure long-range optical links, and optical wireless. Further, we expect that the new seed source, combined with our commercial product line of fiber amplifiers (www.ramphotonics.com/products/spa-fiber-amplifier) that are currently targeted to low-noise amplification of single (solitary) pulses to high pulse energies, will generate a new flexible-format pulsed laser source that can enable new opportunities in sensing, laser accelerator drivers, medical surgery, and ultrafast laser material processing.