Abstract
A novel feedback method for focusing an ultrafast photon source is illustrated for the first time. The method relies on the pulse shape analysis (PSA) of the high-speed transient photocurrent (TP) measured as a function of relative distance between the objective lens and a photosensitive semiconductor device. Space-charge effects due to high-injection conditions result in a screened electron–hole pair plasma which exhibits an erosion time constant which depends on the density and ambipolar diffusivity of the plasma. Focusing the beam increases the average injection level thereby decreasing the ambipolar diffusivity and extending the transient photocurrent. A simple pulse shape analysis of the transient inside a feedback loop is used for optimizing the spot size. In theory, the method can be applied to any technique involving a photon source which delivers an ultrafast pulse which generates high-injection carrier levels when focused. Here, the method is outlined and demonstrated on a Si photodetector optimized for λ = 800 nm.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
