Page History

Some details on the CW laser diode laser (fibre fiber coupled) that we plan to .

The main motivation was its use for the interferometer.This laser could also be used as an E320 interferometer (OAP1 and 2 alignment), but will serve now as general IR alignment laser for FACET S20 in general.

Model: I0785SL0050PA-USB

Central wavelength: 785nm +- 0.5nm.

Power: < 50 mW (Class 3B)

Bandwidth: 109 kHz

Coherence length: 870 m

Image Added

Fig 1: Front view of the laser. Fibre coupled exit (2). Laser on button and light (3).

The laser has a Fig 2: Manual (left) and view of the port for the closed loop interlock (RJ-11 port).

Fiber coupled collimator.

Implementation at S20

Laser enclosure as at B40, with shutter.Collimator details herewith 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 .

Divergence needs to be adjusted to match main laser (find good procedure to do this).

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

Image Added

Fig 3: Identifying suitable spot for the laser between rail setup and SAGA2 (Dec 2021).

Image Added

Fig 4: Laser safety enclosure with laser, fibre and shutter (Dec 2021/Jan 2022).

Image Added

Fig 5: Setting polarisation, beam size and collimation(Dec 2021/Jan 2022).

Image Added

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

Image Added

Image Added

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.

Image Added

A motorised beam block for the CW beam can be found on the same controller on Ch 5.

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.

...

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.