Some details on the CW diode laser (fibre coupled).
The main motivation was its use for the E320 interferometer (OAP1 and 2 alignment), but will serve now as general IR alignment laser for FACET S20.
Model: I0785SL0050PA-USB
Central wavelength: 785nm +- 0.5nm.
Power: < 50 mW (Class 3B)
Bandwidth: 109 kHz
Coherence length: 870 m
Fig 1: Front view of the laser. Fibre coupled exit (2). Laser on button and light (3).
Fig 2: Manual (left) and view of the port for the closed loop interlock (RJ-11 port).
Implementation at S20
Laser enclosure with shutter S3 (LSS) enclosing the full laser (see in comparison enclosure for B40 where only fibre as enclosed).
Using a fibre-coupled collimator F280APC-780 (https://www.thorlabs.com/thorproduct.cfm?partnumber=F280APC-780) to expand to a few mm's (~4 mm?).
The fibre is either P3-780PMY-2 (https://www.thorlabs.com/thorproduct.cfm?partnumber=P3-780PMY-2) or P3-780PM-FC-2 (https://www.thorlabs.com/thorproduct.cfm?partnumber=P3-780PM-FC-2
Then used a X3 beam expander GBE03-B (https://www.thorlabs.com/thorproduct.cfm?partnumber=GBE03-B) to 7 mm FWHM (measured Feb 2022).
Co-injected with the main laser through a polariser.
The beam is spatially overlapped on DMNear/Far or the focal spot camera and DMFar.
The divergence was adjusted using the beam expander such that the beam was brought to focus on DMFar and the focal spot camera.
- Collimation matched with main beam (Jan 2022): http://physics-elog.slac.stanford.edu/facetelog/show.jsp?dir=/2022/05/31.01&pos=2022-01-31T16:29:11
- Spatial overlap with main beam (Jan 2022): http://physics-elog.slac.stanford.edu/facetelog/show.jsp?dir=/2022/01/03.01&pos=2022-01-03T17:25:01
- Update on implementation (Dec 2021/Jan 2022): http://physics-elog.slac.stanford.edu/facetelog/show.jsp?dir=/2022/01/03.01&pos=2022-01-03T10:21:04
- Commissioned successfully in tunnel (Feb 2022): http://physics-elog.slac.stanford.edu/facetelog/show.jsp?dir=/2022/06/10.02&pos=2022-02-10T10:41:38
Fig 3: Identifying suitable spot for the laser between rail setup and SAGA2 (Dec 2021).
Fig 4: Laser safety enclosure with laser, fibre and shutter (Dec 2021/Jan 2022).
Fig 5: Setting polarisation, beam size and collimation(Dec 2021/Jan 2022).
Fig 6: Co-injection of the expanded CW beam with the pulsed beam through polariser.
Motorisation for overlap on DMNear and Far using MF1 and MF2 (see Fig 6).
Can be found under Laser → LI20 → Infrastructure → MOC-LI20_MC06 → Fiber Laser
Switching between pulsed and CW is for now (Feb 2022) done by using the 2nd wave plate.
It is found under Laser → LI20 → Infrastructure → XPS-MOC-LA20-LS24 → Ch2
50 degrees maximises the pulsed beam, 95 degrees (50+45 deg) maximises CW.
Implementation at B40 (deprecated as of Dec 2021)
Laser enclosure as at B40, with a 2" Macor shutter.
To activate the laser one has to push a button on the front panel.
This means one cannot enclose the full laser, but only shutter with the fiber termination.
Some lens tube is used to restrict access to the fiber connectors and to protect the fiber from mechanical damage.
In S20, we enclosed the full laser with the reasoning that we will keep the laser on for extended periods of time, so we will not have to access the button.
