Generating optical frequency combs directly from semiconductor diode lasers
Abstract
The development of optical frequency comb technology revolutionized optical frequency metrology and synthesis, enabled optical atomic clocks and was essential for the generation of isolated attosecond pulses. Further applications are being developed in many areas including chemical, biological and explosives sensing using dual comb spectroscopy, arbitrary waveform generation and signal processing. The explosion of work on frequency combs, which took place approximately 15 years ago, was triggered by the development of techniques to generate combs using bulk-optic mode-locked lasers such as Kerr-lens modelocked Ti:sapphire lasers. Due to their size, delicacy and inefficiency, the use of bulk optic lasers limits the potential applications of combs. While fiber lasers are an improvement on bulk-optic lasers, they are still not Òchip-scaleÓ and struggle to achieve the optimum comb parameters needed for most applications of combs. These drawbacks have been partially addressed by the development of a new type of combs based on nonlinear microresonators. While significantly more compact that bulk optic mode-locked lasers, and potentially Òchip-scaleÓ, these ÒmicrocombsÓ still require substantial, watt-level, pump lasers, often achieved using single-frequency diode lasers to seed a fiber amplifier. One route to achieve a truly chip-scale frequency comb would be to use an electrically pumped semiconductor diode laser. This approach may seem obvious as diode lasers are almost universally used to convert electrical power to optical power in todayÕs combs, be it in bulk optic lasers where diode laser bars are used to pump the laser crystals or in microcombs where diode lasers are used to pump the fiber amplifiers, and often are the original seed source. Thus this route may seem obvious, however there are good reasons why it has not been achieved, namely electrically pumped semiconductor lasers suffer from gain dynamics that are deleterious for short pulse generation, and the phase locking required for generating frequency combs is typically achieved through the production of trains of short pulses. This project addresses the shortcomings of current methods for comb generation by taking fresh and innovative approaches to generating optical frequency combs using electrically pumped semiconductor diode lasers. Comb generation is usually understood to be synonymous with modelocking for short pulse generation, which has proven problematic in diode lasers. Our project leverages two unique and innovative concepts. The first is to generalize the concept of mode-locking and seek devices where mode-locking results in a stable comb, but not short pulses. The second concept is to design and implement new types of ÒmodelockersÓ that can overcome the limitations of traditional modelockers based on real saturable absorption.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 02, 2019
- Source ID
- W911NF1510625
Entities
People
- Steven Cundiff
Organizations
- Army Contracting Command
- Defense Advanced Research Projects Agency
- University of Michigan