Influence of the spectral width and statistics of a Stokes signal on the efficiency of stimulated Raman scattering of nonmonochromatic pump radiation

Abstract

We show that the Einstein-Straus model does not give a robust answer to the problem of the influence of the cosmic expansion on the local physics. This is done by finding the most general static region embeddable in a Friedmann-Lemaître-Robertson-Walker expanding cosmology and showing that the model must be 'almost spherically symmetric'. More precisely, we show that the boundary of the static region must be a 2-sphere at each instant of cosmic time. The motion of this 2-sphere in spacetime is as follows: its 'would-be' centre (if there were no static region) moves along a path whose projection on any 3space of constant cosmic time is a geodesic with respect to the induced 3-metric. The velocity of this geodesic is determined from the matching. In particular, this centre must be at rest with respect to the cosmological flow (thus giving a spherically symmetric model) when any of the standard energy-momentum tensors inside the static region is imposed.

In‐Source High‐Resolution Spectroscopy Using an Integrated Tunable Raman Laser

“…Since these timescales are generally longer than the Raman dephasing time, in most cases we can model the Raman process for each spectral mode using steady-state Raman theory, even if the interference of the pump axial modes produces a time structure that would need transient Raman theory if modeled in the time domain. This computationally-efficient approach has been widely used in the past to analyze SRS with multi-mode lasers, [37][38][39][40][41][42][43] and more recently to model phonon-resonant Raman interactions featuring efficient spectral squeezing in integrated diamond resonators. [32] The interaction of pump and Stokes mode fields can be calculated using non-degenerate mode interactions.…”

The influence of phonon harmonicity on spectrally pure resonant Stokes fields

“…Since the longitudinal modes vary slowly (much slower than the phonon dephasing time, in diamond 6.8 ps), we can use steady-state Raman theory, even if interference of the modes produces structures that would need transient Raman theory if modelled in the time domain. This approach has been used widely used to analyze SRS with broad-band lasers [24][25][26][27][28][29][30], and here we employ this method to model the diamond Raman resonator.…”