Discussion Overview
The discussion revolves around the concept of two-photon absorption (TPA) in silicon, particularly at a wavelength of 1500 nm. Participants explore the conditions under which TPA occurs, its dependence on laser intensity, and seek information regarding the absorption coefficient for silicon.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- One participant inquires about the mechanism of two-photon absorption and whether a Beer-Lambert law applies to this process, specifically seeking the absorption coefficient for silicon at 1500 nm.
- Another participant notes that nonlinear absorption, such as TPA, typically requires very high laser intensities, suggesting that at 1500 nm, the TPA in silica would be negligibly small unless sufficient intensity is achieved.
- A participant mentions using a Tsunami-Opal femtosecond laser source, indicating that it produces a relatively high peak intensity at 1500 nm, which raises the interest in evaluating TPA effects.
- A specific value for the two-photon absorption coefficient in silicon is provided as 0.45 cm/GW at 1540 nm, referencing a study by Tsang et al.
- Another participant expresses gratitude for the information shared.
- There is a clarification regarding the use of the Tsunami-Opal source, with one participant acknowledging a previous misconception about the typical wavelength range for femtosecond pulse generation.
Areas of Agreement / Disagreement
Participants express differing views on the significance of two-photon absorption at 1500 nm, with some suggesting it may be negligible while others believe the conditions may allow for observable effects. The discussion remains unresolved regarding the practical implications of TPA in this context.
Contextual Notes
There are limitations regarding the assumptions about laser intensity required for TPA and the specific conditions under which the absorption coefficient applies. The discussion does not resolve the applicability of the Beer-Lambert law to two-photon absorption.
. I never considered 1500 nm to be within your typical window of femtosecond pulse generation, but it appears I was wrong.