Effects of Neutron Fluence on the Operating Characteristics of Diode Lasers Used in Atomic Frequency Standards
Abstract
One of the next major advances in rubidium and cesium atomic clock technology will center on the use of diode lasers for optical pumping. The atomic clocks used on board satellites have the potential to interact with various forms of radiation that are not present in the laboratory environment, and the effects of this radiation on the laser's operating characteristics relevant to clock applications are not well known. The present report describes an ongoing experiment to study the effects of neutron fluence on the operating characteristics of Mitsubishi Transverse Junction Stripe (TJS) AlGaAs diode lasers. Different models of the TJS diode laser produce optical radiation in both the 780 and 850 nm range, appropriate for optical pumping in rubidium and cesium atomic clocks, respectively. In this phase, a set of TJS diode lasers has been exposed to a neutron fluence of 2 x 1012 n/cm2, and four laser characteristics were examined after each exposure. The laser's light output versus injection current and single-mode linewidth versus output power both influence the efficiency of optical pumping and hence the atomic clock's signal- to-noise ratio. We have also measured the laser's single-mode wavelength versus injection current (laser tuning). Since the diode laser must remain tuned to the appropriate atomic transition, any degradation in the ability to tune the laser will impact atomic clock reliability. Finally, the diode laser's gain curve has been studied at several injection currents below threshold. This diode laser characteristic is taken as an indicator of the neutron damage mechanisms in the laser's semiconductor material. Changes in these characteristics due to the neutron exposure are reported.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 15, 1990
- Accession Number
- ADA226763
Entities
People
- C. E. Barnes
- James C. Camparo
- Robert P. Frueholz
- S. B. Delcamp
Organizations
- The Aerospace Corporation