Acoustical and 1∕f noises in narrow linewidth lasers

Optical Fiber Spool Acoustic Wave Resonances Employing a Mach-Zehnder Interferometer in Vacuum Chamber

“…In our case we used an FFT span of 200 Hz. The obtained laser white noise PSD flat level [46] of -82 dBVRMS /√Hz (shown in Fig. 3) is well above the noise level (without light) of -105 dBVRMS /√Hz (not shown here).…”

“…3) is well above the noise level (without light) of -105 dBVRMS /√Hz (not shown here). This small noise level at 1.2 Torr is equivalent to 60 nW/√Hz and the laser PSD level is 12 W√Hz [46].…”

“…2) is necessary to decrease the acoustical noises and to obtain the sharp resonances peaks shown in Fig. 3 [46]. The results without vacuum are inaccurate and it is almost impossible to distinguish the specific resonances [46].…”

“…Also, this chamber and the laser were mechanically isolated from the environment by double isolation optical tables. At 1.2 Torr, the environment noise was around 23 dB below the signal level [46]…”

Narrow-Linewidth Laser Linewidth Measurement Technology

“…However, the center frequency v b of the beat notes is 0 Hz; therefore, the low-frequency noise in the environment interferes with the measurement results. Considering the sensing characteristics of the optical fiber [40], the disturbance of environmental noise, temperature, pressure, and other factors can seriously affect the test results obtained by the optical fiber [41].…”