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d2:dbr_laser [2018/11/09 19:06] – [Inputs, Outputs, and Controls] Michael Radunskyd2:dbr_laser [2019/09/24 21:26] – [Description] Michael Radunsky
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 =====Description===== =====Description=====
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 +<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.  |
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 +</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.
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 |Stage 2 Temperature of DBR Laser Diode|>15°C and <40°C| |Stage 2 Temperature of DBR Laser Diode|>15°C and <40°C|
 |Laser Diode Current|See datasheet included with your laser.| |Laser Diode Current|See datasheet included with your laser.|
 +</WRAP>
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 +<WRAP center round important 60%>
 +The laser should never be operated at a temperature below the dew point temperature for your laboratory conditions.  Condensation can form on the laser chip and/or mounting hardware resulting irreparable damage.
 </WRAP> </WRAP>
  
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-=====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]]. +
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-<imgcaption DBR_lock_screws|Lock screws and beam pointing controls> +
-{{ :d2:d2-100:dbr-lock-screws.png?nolink&300 |}} +
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-</imgcaption> +
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-**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:
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 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.
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-=====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.txt · Last modified: 2022/09/08 21:50 by 127.0.0.1