User Tools

Site Tools


d2:dbr_laser

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision
Previous revision
d2:dbr_laser [2019/05/17 12:36]
Michael Radunsky [Absolute Maximum Ratings]
d2:dbr_laser [2019/09/24 14:26] (current)
Michael Radunsky [Description]
Line 17: Line 17:
  
 =====Description===== =====Description=====
 +
 +<WRAP center round box 60%>
 +| {{ :​warning-sign.png?​200&​nolink }}    | The D2-100 laser module is factory aligned. ​ It is not advised that the user attempts to re-align the laser in the field. ​ If the laser becomes misaligned, please return the unit to the factory for realignment. ​ |
 +
 +</​WRAP>​
  
 The DBR laser module is comprised of a distributed feedback (DBR) laser diode in a precision temperature-controlled housing with beam conditioning optics and an optical isolator. ​ DBR laser diodes are fabricated with the feedback grating patterned directly over the gain section of the diode. ​ They are highly immune to vibrations and by virtue of a very short cavity (~ 1 mm), they can be current tuned over more than 50 GHz.  The result is a robust laser capable of very fast servo control for easy locking to atomic transitions. ​ The module contains no moving parts or piezo-electrics and is therefore inherently robust and rugged. The DBR laser module is comprised of a distributed feedback (DBR) laser diode in a precision temperature-controlled housing with beam conditioning optics and an optical isolator. ​ DBR laser diodes are fabricated with the feedback grating patterned directly over the gain section of the diode. ​ They are highly immune to vibrations and by virtue of a very short cavity (~ 1 mm), they can be current tuned over more than 50 GHz.  The result is a robust laser capable of very fast servo control for easy locking to atomic transitions. ​ The module contains no moving parts or piezo-electrics and is therefore inherently robust and rugged.
Line 76: Line 81:
  
  
-=====Inputs, Outputs, and Controls=====+=====Laser Control Signals=====
  
-**Vertical and horizontal pointing ** +==== Temperature Control Loops ====
- +
-The vertical and horizontal alignment of the laser system is factory set and should not need adjustment. ​ However, if your specific application requires it or the system is misaligned, the DBR subassembly has adjustments to steer the beam for alignment to the spectroscopy module or other modules. ​ The beam pointing is adjusted by loosening the three lock screws ½ turn past the crack point and adjusting the x and y positioning set screws on the top and left side (facing out along the laser beam) of the module (see <imgref DBR_lock_screws>​). For more detailed instructions,​ see  the [[#​aligning_the_dbr_laser_module|alignment section]]. +
- +
- +
-<​imgcaption DBR_lock_screws|Lock screws and beam pointing controls>​ +
-{{ :​d2:​d2-100:​dbr-lock-screws.png?​nolink&​300 |}} +
- +
-</​imgcaption>​ +
- +
- +
-**Beam Conditioning** +
- +
-The collimation of the output beam is set at the factory and should not be adjusted unless absolutely necessary. ​ Remove the isolator subassembly from the baseplate with the 4 screws accessible from the bottom. ​ The collimation can be adjusted by turning the lens.  A spanner wrench can be inserted into the two holes on the side of the black lens holder to adjust the lens.   +
- +
-Laser diodes all have astigmatism,​ which means the horizontal and vertical axis have different foci.  Vescent uses a powerful asphere with a short focal length and an anamorphic prism pair to create a small diameter circular beam. This reduces the costs of the isolator and other downstream modules by reducing the clear aperture requirements. ​ While the aspheres and anamorphic prisms produce a circular beam, astigmatism dictates that a single lens will not simultaneously collimate both orthogonal axes of the beam with the result that in the far field the beam is again elliptical. +
- +
-The far-field pattern is the most important for ascertaining the quality of the diode output. ​ The near-field pattern often shows stray light from the diode waveguide and ASE that doesn'​t propagate as part of the primary beam.  However, aberrations and beam clipping due to an insufficient lens NA will show up as fringes-on the far field pattern. ​ Vescent has taken care in the design of the DBR laser module to keep aberrations and clipping to a minimum, resulting in a clean beam in the far field. +
- +
-**Cable Connector**+
  
 The connections to the TECs and thermistors are made to an 8-pin Hirose connector (see <tabref TECconnectortable>​ for identity of connectors). ​ The pin definitions are: The connections to the TECs and thermistors are made to an 8-pin Hirose connector (see <tabref TECconnectortable>​ for identity of connectors). ​ The pin definitions are:
Line 127: Line 113:
 NOTE:  Earlier models use a push-pull connector for the 8-pin connector to the DBR module. ​ To remove take care to apply opposition forces with the thumb and forefinger knuckles against the housing. ​ Excessive force could displace the output beam and require realignment. NOTE:  Earlier models use a push-pull connector for the 8-pin connector to the DBR module. ​ To remove take care to apply opposition forces with the thumb and forefinger knuckles against the housing. ​ Excessive force could displace the output beam and require realignment.
  
-**Laser Current (SMA)**+==== Laser Current (SMA) ====
 <WRAP center round important 60%> <WRAP center round important 60%>
 Never connect or disconnect the D2-100 Laser to a laser controller that is energized. ​ Always power down the laser controller completely before making connections to this laser. Never connect or disconnect the D2-100 Laser to a laser controller that is energized. ​ Always power down the laser controller completely before making connections to this laser.
Line 139: Line 125:
  
  
-=====Aligning the DBR Laser Module===== 
- 
-The module should not need adjustments,​ but if necessary the following procedure can be used to fine tune the beam positioning. 
  
-  - Loosen the three locking screws on the back of the DBR module ½ turn past the crack point. 
-  - With a 0.050" Allen driver, adjust the vertical adjustment setscrew on the top of the DBR housing to level the beam. 
-  - Adjust the horizontal adjustment 4-40 set screw on the left side of the DBR housing (See <imgref DBR_lock_screws>​). 
-  - Alternatively,​ use the spectroscopy module as a beam target. ​ Place the spectroscopy module as far down the table as possible, bolt it down, and center the beam to the input hole. 
-  - Gently retighten the three locking screws. 
  
d2/dbr_laser.1558121762.txt.gz · Last modified: 2019/05/17 12:36 by Michael Radunsky