Lasers

Various laser launches can be used with diSPIM. Below find notes specific to each one.

In normal diSPIM use the laser launch will be controlled using its digital TTL inputs. The Tiger controller's PLC card will be generating those signals, which will turn the lasers on/off at the appropriate times and selecting the correct side. For information on connecting the cables see the appropriate section of the manual. The analog intensity is generally static during the experiment and so can be controlled using the high-level software (Micro-Manager or vendor's software) over a USB or serial connection; there may be some enabling that needs to happen using the high-level software. If analog intensity must be controlled during an experiment then ASI can provide a separate Tiger card which can drive the laser's analog inputs.

In general the laser power requirements are very modest, e.g. you only want at most a few mW of optical power at the sample. So no need to pay for lasers with extra power.

For a dual-view system it is helpful to have a laser launch with dual outputs. That way the entire laser intensity can be switched between the two paths since only one path is used at a time. Such launches are not common but multiple options are commercially available (see below).

If you don't use a laser launch with dual outputs you have two basic approaches: (1) split the beam passively or (2) insert an active switch.

First, you can passively split the beam into two fibers and rely on the unused scanner to blank its beam at any given point in time. The scanner gives decent but incomplete blanking (up to 0.1% bleed-through). Fiber splitters are inexpensive and compact but the split ratio depends on wavelength so this doesn't work for multi color. You can split into 2 paths in free space on an optical table before fiber coupling, which requires some expertise but allows a 50/50 split across wavelengths. ¹⁾ When using an optical table it's possible to insert shutters to fully block the beam. ASI is prototyping a compact self-contained beamsplitter. Passively splitting the beam reduces the intensity by at least a factor of 2 (more with losses) but normally that isn't a problem because light sheet imaging usually uses very low intensities.

Second, you can add a galvo or 1×2 switch between the laser output and the two scanners. Leoni makes a commercial switch with male fiber inputs and outputs. You will need to couple the laser's fiber with the switch's input fiber, e.g. with a butt-coupler and its attendant losses and possible degradation over time. You could also find a vendor to do fiber splicing. Another option is to to free-space switching using a galvo or similar on an optical table. There may be other switching options available, if you know of one please add it to this wiki! Active switching usually involves some loss but generally speaking you can keep more than 50% of the input intensity.

Below are notes about commercial laser launches that have been used with diSPIM.

Vendor's brochure for MLE-L.

• Special dual-output version available on request
• choice of multiple laser lines installed at factory
• automatic alignment feature makes setup easy even after shipping
• very compact form factor compared to other launches
• fibers have NA ~0.06
• 50 ohm SMB inputs for each laser on/off, version with switch has high impedance BNC input for fiber select built into interlock cable

• Use Toptica MLE device adapter. Fairly full-featured and supported by Toptica.

(no info seems to be available online but similar to LLM5 with dual output option)

• has dual output option
• form factor similar to large desktop computer
• choice of multiple laser lines installed at factory
• fibers have NA ~0.12
• high-impedance inputs for each laser on/off and side select on DB-15 connector (ASI can provide breakout cable to BNC)

• use the LLM5 device adapter (not maintained by manufacturer)
• doesn't support the intensity scale factor but otherwise should be fine
• switcher shows up as a fake wavelength in property browser

• dual-output version available
• quite bulky form factor compared to other launches
• high impedance inputs for each laser on/off and side select
• not possible to have intensity selected by software while on/off triggering done by hardware ⇒ added complexity in driving analog inputs

• Must take care to get master blanking signal correct
• Because of all-or-nothing external control, must have means to provide analog intensity control (not needed with any other launch)

• device adapter present??

• separate OBIS lasers and Galaxy combiner allow in-field addition or substitution of lasers
• possibly available with Leoni switch already fiber-spliced

• Use OBIS device adapter (not maintained by manufacturer)
• As of Nov 2015, device adapter only works with single-line OBIS; with the multi-line box only the laser in the first position can be controlled

• multi-fiber output module available (“FiberSwitcher”)
• generally sold by 3i intended to be used with their Slidebook software
• has high impedance inputs for each laser on/off and side select
• has analog intensity inputs

• Probably would work if you had way to control intensity, e.g. by DAC card.