The layout of the primary optics

This new compressor layout has been implemented and completed in May 2022. The new layout is a streamlined design, simple, robust, and user-friendly. It has decoupled the time-tool beam. So with time tool overhaul and the new standard configurations, it has executed the PEMP goal successfully in 2022. The new compressor features are listed below:

• Remote controls of grating angle: in the new system, two new rotation motors (URS75BPPV6) for both gratings (Fig1: G1 & G2) were installed to replace the manual controlled rotation stage. The translation stage on G2 was also replaced by LTA, which is encoded and remote-controlled. With all remote-control capabilities, we will implement an in-situ autocorrelator for an auto-optimization procedure, which can be operated with python script.
• Beam path: the beam incidents at the lower beam height in the compressor chamber. The beam goes to G1, G2, retro mirror (to the higher beam height), G2, G1, M1, M2, M3, and then goes to the target chamber. 
• Input/output pointing alignment: for the input alignment, we have two mirrors, T3 and M0 to adjust the beam incident angle to center on two irises, I1 and I2. For output alignment, we use two mirrors, M1 and M2 to center on I3 and I4. For target chamber alignment, we use M2 and M3 to center on I5 and target chamber reference (far-field image) or near-field/far-field imagers in the target chamber.
• Grating parallels: we check grating parallel by setting up a plumb bar near I2 to check the overlap of the shadow on the incident and outgoing beam. 
• Compact mounts: in the new system, we use the 5” in-house designed mirror mounts to replace the 6” ones with lots of disadvantages. We also use compact TRA6 motors to replace LTA motors (cumbersome as pointing motors). As shown in Fig 2, The controls of M1x, M1y, M2x, M2y, M3x, M3y, G1 rotation, and G2 rotation are on Newport XPS_1 (mcn-mec-las1). The control of G2 translation is on Newport XPS_2 (mcn-mec-las2).
• Decouple time-tool: in the old system, the time tool beam was leaking through the compressed beam. It created complexity for both alignment and operation. In the new system, time-tool beam is decoupled from this line.
• Upgraded grating mounts: the grating mounts are redesigned with better stability and compactness. It comes with three leaf springs to support grating via radial groove allowing clocking adjustment, and the manual actuator in the back for tilt adjustment (Fig3). 

Image Added   

Figure 1. the new layout design: the beam impinge upon the first diffraction grating immediately after entering the vacuum window, from which the beam pointing can be monitored. There are three motorized mirrors M1, M2, and M3 after the fourth bounce of the grating pair G1 and G2 to provide full pointing control prior to propagating into the target chamber.

Image AddedImage Added

Figure 2. The controls of M1x, M1y, M2x, M2y, M3x, M3y, G1 rotation, and G2 rotation are on Newport XPS_1 (mcn-mec-las1). The control of G2 translation is on Newport XPS_2 (mcn-mec-las2).

Image Added

Figure 3. upgraded grating mounts: 1. three leaf springs hold the grating via radial groove allowing clocking adjustment. 2. the grating mount sits on the rotation stage (URS75BPPV6) and positions the grating surface on the rotation axis precisely.  3. the LTA motorized stage is the base. 4. the manual actuator on the back allows tilt adjustment. 

Layout of diagnostics

In the new compressor system, a complete set of beam pointing imagers are installed to assist the alignment remotely. An online single-shot autocorrelation (SSA), TIPA, is designated for the real-time pulse duration measurement as shown in Fig. 4.

• Input/output pointing imagers:  For the input, CompInFF, CompInNF, and CompG2 are monitoring the far field image behind the 3x telescope, near field image behind the deformable mirror, and the beam pointing on G2. Remotely, SM8 (smartact 8) will be used to center the beam on CompInFF and CompInNF. If the beam pointing is still off on CompG2, M0 can be used to adjust. We also have two cameras (Fig. 2 near field and far field) looking at compressor output. We have three motorized output mirrors (M1, M2, and M3)for adjustment. For output pointing, CompOutNF and CompOutFF are near-field and far-field imagers for output beam after the compression. M1 and M2 can be used to center the beam pointings on CompOutNF and CompOutFF. M3 is used to center the beam to the target chamber reference. 
• Real-time SSA: 1% leak through M2 (99% R mirror) is directed through a side window, a downsize telescope and a 1/2 waveplate into TIPA. The autocorrelation trace can be detected with either MPA1 or MPA2 amplified beam onto a GigE camera. The intensity can be adjusted by 1/2 waveplate. The chirp induced by the glass media (M2, window, and telescope) is measured to be -0.6 mm in the amount of G2 translation. For example, if we obtain the shortest pulse at 11.45 mm G2 translation, the real shortest pulse should be at 11.45-0.65=10.95 (mm). The measurement detail is shown in Fig. 5.

Image Added

Figure 4. a complete set of input/output pointing imagers are installed to assist the alignment remotely. An online single-shot autocorrelation (SSA), TIPA, is designated for the real-time pulse duration measurement.

Performance data

• TiPA measurement: The measurement was done with the latest setup as shown in Fig.4 by TIPA. 1% leak through M2 (99% R mirror) is directed through a side window, a downsize telescope, and a 1/2 waveplate into TIPA. The autocorrelation trace can be detected with either MPA1 or MPA2 amplified beam onto a GigE camera. The intensity can be adjusted by 1/2 waveplate.

• • Glass-induced chirp: The plot shown in Fig. 5 is the pulse duration as a function of G2 translation scan. The glass-induced chirp (M2, window, lenses, and waveplate) can be measured by comparing the scans with and without glass media (solid green and empty green) in the air. The lowest point shifting from 12.05 to 11.45 mm suggests that the glass-induced chirp is -0.6 mm in G2 translation.  
  • Vacuum-induced offset: when the chamber is pumped down, the shortest position can be offset due to the removal of air and the breadboard stretch. It turns out the air contribution (um scale)  is much less than the breadboard stretch. We can find out the offset amount by comparing the scans in the air and in the vacuum (solid green and solid red). The lowest point shifting from 12.05 to 11.45 mm suggests that the offset is -0.6mm in G2 translation. 
  • In practice, if we obtain the shortest pulse at 11.45 mm G2 translation, the real shortest pulse should be at 11.45-0.65=10.95 (mm). 

Image Added

Figure 5. 

• SSA measurement
  • sweet figure
• SPIDER measurement
  • sweet figure