Newport N-STP-910 User manual

1791 Deere Avenue
Irvine, California
92606 USA
www.newport.com/contact-us
______________________________________________________________________________________
[phone] | Newport Corporation | www.newport.com
Stabilized Single Frequency Laser
Operating Manual
Models N-STP-910, N-STP-912
L10698-2 REV: 1.21.7 NPT

NOTICE: This manual contains specifications, descriptions, and drawings for the Newport stabilized
Helium Neon laser systems.
Product specifications contained in this manual are subject to change without prior notice. Newport
Corporation will not be responsible for errors or omissions in this manual, or for incidental or
consequential damages in connection with the furnishing or use of this information.
This document may not be photocopied, duplicated, or reproduced by any means without the prior
written consent of Newport Corporation.
Comments or suggestions regarding this manual are appreciated and should be sent to the following
address:
Newport Corporation
1791 Deere Avenue
Irvine, California, 92606 USA
Attention: Customer Service
Phone [phone]
www.newport.com/contact-us
Publication date: January 11, 2021
©2021 Newport Corporation
[phone] | Newport Corporation | www.newport.com

Model N-STP Operation Manual
Table of Contents
Content
Page
1.0 Conventions Used in This Manual
2
2.0 Laser Safety and Precautions
3
2.1 CDRH Regulations
4
2.2 Power Source and Grounding
4
2.3 RoHs Compliance
5
3.0 Installation Instructions
6
3.1 Initial Inspection
6
3.2 Grounding
6
3.3 Operating Environment
6
4.0 Operating Instructions
7
4.1 Assembly and Switching On
7
4.2 Explanation of Controls and Indicators
8
4.2.1 AC/DC Converter
8
4.2.2 Laser Power Supply Remote Connector
9
4.2.3 Stable (Green) Indicator
10
4.2.4 Over Temperature (Red) Indicator
10
4.2.5 Output Adjust
11
4.2.6 Principle of Operation
11
4.2.7 Output Adjust and Operations Check
13
5.0 Preventive Maintenance
13
6.0 Operating Specifications
14
6.1 Laser Head Mounting
16
7.0 Output Power / Frequency Function
17
8.0 Frequency Calibration
18
9.0 Troubleshooting
19
10.0 Warranty
21
1

Model N-STP Operation Manual
1.0. Conventions Used in This Manual
Throughout this manual you will find information that is separated from the regular
text by lines and labeled by an icon in the margin. Lasers are potentially dangerous
devices, and some of this information is vital for your safety. The significance of the
notations is explained below.
Lasers are electrical devices and improper use can expose the operator or others
to potentially lethal voltages. The “Hazard” icon, represented by a triangle with a
lightning bolt, identifies precautions needed to avoid electrical injury or damage to
the equipment.
The series of laser systems which are covered by this manual are classified as
Class II and IIIa devices as defined by the Center for Devices and Radiological
Health of the United States Food and Drug Administration and Class 2 and 3R
devices as defined by IEC 60825-1. The “Caution” icon, represented by a triangle
with laser burst, identifies precautions needed to avoid eye injury to anyone in the
area.
The “IMPORTANT” icon, represented by a triangle with an exclamation point,
indicates information that is particularly important to the optimum performance of
the laser system or information about the procedure or topic under discussion.
The following acronyms are used in this manual:
CDRH Center for Devices and Radiological Health
cw Continuous Wave
FCC Federal Communications Commission
IEC International Electrotechnical Commission
OEM Original Equipment Manufacturer
The following abbreviations and symbols are used in this manual:
ac alternating current
dc direct current
in inch
mm millimeter
Vac Volts ac
Vdc Volts dc
kVdc kilovolt dc
W Watt
mW milliwatt
A Amp
mA milliamp
nm nanometers
mrad milliradians
MHz Megahertz
g acceleration
2
IMPORTANT

Model N-STP Operation Manual
2.0. Laser Safety and Precautions
•Avoid eye exposure to either direct or reflected beam radiation
•Do not place reflective components in the beam path
•Do not place reflective components or laser sources at or near eye-level
•Always wear appropriate protective eyewear during operation
•Devices should be operated only by personnel who are properly trained in laser safety
protocol for the device classification in use.
•Laser light is bright and blinding –do not shine at aircraft or vehicles at any distance
Never look directly into the beam of the laser system.
One of two labels (a caution label or a danger label) is attached to the standard laser head
to warn operators of the potential hazards. These labels are illustrated in Figure 1-1.
Figure 1-1. Standard Caution and Shipping Labels
3
LASER LIGHT
DO NOT STARE INTO BEAM
CLASS II LASER PRODUCT (CDRH)
CLASS 2 LASER PRODUCT (IEC 60825-1:2014)
1mw MAXIMUM AT 632.8nm
LASER LIGHT
AVOID EXPOSURE TO BEAM
CLASS IIIa LASER PRODUCT (CDRH)
CLASS 3R LASER PRODUCT (IEC 60825-1:2014)
5mw MAXIMUM AT 632.8nm
COMPLIES WITH CDRH 21 CFR
1040.10 AND IEC 60825-1:2014
COMPLIES WITH CDRH 21 CFR
1040.10 AND IEC 60825-1:2014
N-STP-910
N-STP-912

Model N-STP Operation Manual
2.1. CDRH Regulations
The N-STP series laser systems are CDRH certified according to the rules and
regulations as outlined in part III of the Department of Health and Human Services,
21 CFR Parts 1000 and 1040 for laser products.
Under these guidelines, the Model N-STP-912 conforms to Class IIIa (IEC 3R)
certification, which allows maximum output power of up to 5mW continuous
radiation at a visible wavelength of 633nm. The Model N-STP-910 conforms to Class
II (IEC 2), which allows maximum output power of up to 1mW. Other requirements
include the use of special labeling, an external mechanical beam attenuator, and a
pilot light indication during operation.
The N-STP laser system is shipped from the factory with the necessary features to
conform with the above regulations. These features are recorded for each individual
unit and reported per CDRH regulations under the Accession number 9320815.
Detailed information on these requirements may be obtained at:
www.fda.gov/radiation-emitting-products/
2.2. Power Source and Grounding
The N-STP series laser system includes either the N-STP-910 or N-STP-912 laser head
attached to the single frequency adapter (SFA). They are supplied with the
appropriate AC/DC converters and power supplies for the line voltage requested.
Both the AC/DC converters and power supplies are supplied with grounding
connections so the laser head and adapter housing are grounded when they are
plugged into the appropriate wall outlet.
Under no circumstances should the ground be defeated.
Both the laser head and single frequency adapter (SFA) can be powered from a single
source of 15 VDC when using an optional OEM style 15VDC input laser power supply.
Please contact the factory for further details regarding this option.
Verify the power common is at ground potential.
4
WARNING

Model N-STP Operation Manual
2.3. RoHS Compliance
ROHS-3 DIRECTIVE 2015/863/EU
The products covered by this manual comply with RoHS 3, Directive (EU) 2015/863, which adds 4 phthalates to
previous RoHS 2 Directive 2011/65/EU. Specifically, the products containing the substances listed below are in
concentrations below the MCV or are exempt. The products are therefore understood to be in compliance with
Directive (EU) 2015/863 of the European Parliament and the Council of 4 June 2015 on the restriction on the use of
certain hazardous substances in electrical and electronics equipment (RoHS Directive) in accordance with the
definitions set forth.
Newport Part Numbers: N-STP-910 N-STP-912
Substance
Compliance Reason
Lead (Pb)
The subject product does not contain substances in excess of the maximum
concentration values tolerated by weight in homogeneous materials as listed in
Annex II of the Directive, or per directive 2011/65/EU, Annex III, are exempted
from the Restriction in Article 4(1), per 7(c)-I: “Electrical and electronic
components containing lead in a glass or ceramic other than dielectric ceramic
in capacitors.”
Mercury (Hg)
There is no intentional use
Cadmium (Cd)
There is no intentional use
Hexavalent Chromium (Cr+6)
There is no intentional use
Polybrominated Biphenyls (PBB)
There is no intentional use
Polybrominated diphenyl ethers (PBDE)
There is no intentional use
Hexabromocyclododecane (HBCDD)
There is no intentional use
Bis (2-Ethylhexyl) phthalate (DEHP)
There is no intentional use
Dibutyl phthalate (DBP)
There is no intentional use
Benzyl butyl phthalate (BBP)
There is no intentional use
Diisobutyl phthalate (DIBP)
There is no intentional use
China RoHS
This declaration is based on information obtained from suppliers and/or analytical material testing. The manufacturer
makes every reasonable effort to ensure the accuracy of this information as of the date of publication. This declaration
of conformity is used under sole responsibility of the manufacturer and is valid unless superseded by a revised
certification at a later date.
5

Model N-STP Operation Manual
3.0. Installation Instructions
Do not energize system before reading the following sections.
3.1. Initial Inspection
Check the contents of the shipping container for any signs of damage that may
have occurred during transportation. If the contents are damaged, a claim
should be filed immediately with the carrier and the manufacturer in order to
facilitate the repair or replacement.
3.2. Grounding
Before operating the laser system, the system must be connected to a protective
earth ground conductor via the three-prong plug. The plug must be inserted into
an outlet containing a protective earth contact.
Any interruption of the earth ground may result in high voltage being present
on the laser housing.
3.3. Operating environment
The N-STP frequency stabilized laser system may be safely operated in any
orientation. However, operation should be discontinued if condensation forms
on any part of the system. This is likely to occur when the system is brought from
a cold to a warm environment.
Condensation may cause electrical shock if the housing is not properly grounded.
Even if proper grounding is provided, operation in the presence of condensation
may cause irreparable damage to the laser head.
6
WARNING

Model N-STP Operation Manual
4.0. Operating Instructions
4.1. Assembly and Switching On
The single frequency adapter (SFA) mates with the N-STP-910 and N-STP-912 laser heads. The
SFA and laser head are pre-assembled, calibrated and tested for optimum performance by
Newport and should not be taken apart. The unit contains no user serviceable components.
Disassembly of the unit may result in exposure to laser light or hazardous voltages as well as
damage to the laser head or SFA. Unauthorized service will void the warranty.
The orientation of the laser head in relation to the SFA has been precisely adjusted and should
not be changed. The arrow on the laser head should align with the indent on the SFA (Figure
1-2).
Figure 1-2. Plane of Polarization
Connect and operate the system in the numerical order as shown in Figure 1-3. Connect the
main line voltage in accordance with Section 3.2. Confirm that the line voltage switch on
the laser power supply (1) is set for your AC voltage. An improper setting can destroy the
laser power supply and/or damage the laser.
Find and observe the output beam with a white card or piece of paper. The beam intensity
should noticeably increase and decrease in power initially at about once every two seconds
and then at a slower rate as the unit warms-up. For the N-STP-910, the minimum power will
generally be zero. Do not mistake this behavior for the laser turning off.
Application of power to the single frequency adapter (SFA) in excess of 5 minutes with the
laser head deenergized may damage the single frequency adapter.
The “Stable/OT” Green light should illuminate in approximately 5 to 10 minutes indicating
that the unit has reached operating temperature and has stabilized.
7
IMPORTANT

Model N-STP Operation Manual
Figure 1-3. System Connection and Operation
4.2. Explanation of Controls and Indicators
4.2.1. AC/DC Converter
The AC/DC Converter is supplied with an AC cord with proper grounding, along
with an ON/OFF switch and a visual indicator light indicating that 15 VDC is
available at the male output plug of the converter. The AC/DC converter can
accommodate voltages from 90 to 265 VAC at 50 to 60 Hz.
8

Model N-STP Operation Manual
4.2.2. Laser Power Supply Remote Connector
Mains voltage (115 VAC or 230 VAC) is present on remote connector terminals when power
supply key switch is in the “I” (on) position. The power supply must be switched to the “O” (off)
position and disconnected from mains power before removing the remote connector plug
from the socket.
The remote connector is provided as a safety feature to allow remote actuation of the laser
power supply. It must be connected to the power supply rear panel for the laser system to be
enabled. If remote actuation is desired, ensure that the cable and remote switch are rated for
the specified power supply input voltage and current. The remote switch will actuate the
power supply only when the main power switch is switched on (“I”). As supplied, the polarized
remote connector plug is wired with an internal jumper. If the connector is to be used with a
remote external switch, modify the plug as follows:
1. Switch off power and disconnect power supply from main power.
2. Remove remote connector plug from socket on power supply rear panel by pulling straight
out.
3. Press out silver-colored locking pin. Do not discard pin.
4. Remove plug shell.
5. Remove vinyl cap covering plug terminals.
6. Remove shorting wire from plug terminals.
7. Slide the plug shell onto remote connector cable.
8. Solder cable leads to plug terminals.
9. Slide the plug shell back on to plug.
10. Install locking pin removed in step 3.
11. Insert connector into socket on power supply rear panel.
If the laser system is not operated in accordance with these instructions, the function of
essential safety features will be impaired. The laser system has no user serviceable parts within
and requires no user maintenance.
9
IMPORTANT

Model N-STP Operation Manual
4.2.3. Stable (Green) Indicator
When the N-STP series laser system has attained proper operating temperature, the
“Stable/OT” light is energized (green) indicating that closed loop output control is in
operation, see Figure 1-5. The “Stable/OT” light may extinguish briefly under the
following conditions:
•During the initial 20 minutes warm-up period.
•During ambient temperature changes beyond the 10C operating
temperature range.
•Significant temperature changes to the laser head housing caused by
mounting to a large thermal inertia after the unit has been through the
warm-up period.
•Excessive optical cavity feedback due to back reflections from optics in
front of the laser or outside instruments reflecting the beam back into the
system.
Long term optical feedback (i.e. back-reflections into the laser) resulting in the inability
of the SFA to maintain closed loop operation can result in laser and/or SFA failure.
4.2.4. OT (Red) Indicator
The same LED which energizes “green” indicating that the unit has reached stable
operation may energize “red” when the following conditions prevail:
•Power to laser head switched off with power applied to SFA.
•Failure of laser head to reach reference output power.
•Failure of single frequency control to close output control loop.
For all these, the “red” light indicates that the mirror mount has reached its maximum
allowable temperature limit and the energy to the induction coil has been shut down.
If this condition is not addressed, the SFA will cycle between the reset and maximum
temperature limit. This will be indicated by the LED changing between its “green” and
“red” indication.
10
IMPORTANT

Model N-STP Operation Manual
4.2.5. Output Adjust
A multi-turn potentiometer is accessible from the front right side of the adapter, see
Figure 1-5.
Adjustment should only be made with a plastic tuning screwdriver.
Full clockwise (CW) adjustment will increase the output power to typically 1.05mW
for the N-STP-912 or 0.7 to 0.9mW for the N-STP-910 or within 400MHz of the center
line frequency, see Sections 7.0 and 8.0. Full counter-clockwise (CCW) adjustment will
decrease the output power to typically 0.5mW for the N-STP-912 or 0.35mW for the
N-STP-910, see Sections 7.0 and 8.0 for how this adjustment affects the optical
frequency. Each direction is torque protected (associated with a clicking sound) so
that further rotation will result in no power change.
4.2.6. Principle of Operation
The N-STP single frequency laser system works on the principle that a Doppler
Broadened TEM00 output mode can be varied in power and frequency if the cavity
length (distance between laser mirrors) can be controlled. In most single frequency
lasers, heat conduction is used (usually over the entire cavity length) to expand and
thus control the cavity length. The N-STP lasers are unique in that they use induction
heating to control the length of a specially designed mirror mount structure. In this
way, a much smaller package can be accommodated, and more importantly, this
technique allows for faster servo response Figure 1-4 depicts the schematic block
diagram of the induction servo control circuit.
11
IMPORTANT

Model N-STP Operation Manual
Model N-STP-910/912
SWITCHING
POWER SUPPLY
LASER TUBE
SFA ADAPTER
POLARIZER
BEAMSPLITTER
“p” & “s”
“p”
“p”
“s”
PIN DETECTOR
FEEDBACK AMP
A1
RF
AMP
MODULATOR
A2
+
-
OUTPUT ADJUST
ERROR AMP
IN
OUT
C
OPERATION
TEMPERATURE
DETECTOR
OVER
TEMPERATURE
SHUTDOWN
STABLE/OT
INDICATOR
GREEN
RED
Figure 1-4. Schematic Block Diagram
When the SFA is mated to the Models N-STP-910, or N-STP-912 laser head, the output
beam passes through two conditioning optics. The polarizer blocks the unwanted
mode (“s” component) while allowing the “p” component to pass. The beamsplitter
samples a portion of the “p” component for use as feedback to the control circuit.
Since the beamsplitter is also highly polarization sensitive, this tandem arrangement
allows for very high polarization extinction (typically greater than 1000:1).
A high-quality PIN detector is used to convert the sampled “p” component into an
electrical current which is amplified by A1. A2 is a simple gain compensated error
amplifier which provides the necessary error signal to the modulator. The modulator
in turn drives an RF amplifier which couples up to 10 watts of power to the mirror
mount via the induction coil. The mirror mount temperature, typically maintained at
about 80C, is monitored by a temperature detection circuit that controls the feedback
signal to the error amplifier A2. Should the mount fall below a predetermined
temperature, the feedback signal is removed from A2 providing full power, resulting
cavity expansion. Within the predetermined temperature range, (indicated by the LED
being green) feedback is restored to A2 and the circuit locks in the single mode output.
12

Model N-STP Operation Manual
An over-temperature shutdown circuit is configured to remove power to the mirror
mount if for some reason the output power control circuit fails to maintain closed
loop control. When this temperature limit is reached, a “red” LED indication occurs.
4.2.7. Output Adjust and Operation Check
After the normal warm-up period, the output may be adjusted via the output adjust
potentiometer. Carefully adjust the screw full clockwise and note that the output
power attains at least 1mW for the N-STP-912 or 0.80mW for the N-STP-910. Next,
adjust the screw fully counter-clockwise and verify that the output power decreases
to less than 0.70mW for the N-STP-912 or 0.40mW for the N-STP-910. By adjusting
the power over this range, the absolute frequency is also adjusted. In the case of the
Model N-STP-912, this output frequency span corresponds to about 50 to 600MHz
and for the N-STP-910, it corresponds to about 400 to 600MHz from the neon gain
center. There is more on optical frequency adjustment and calibration in Section 8.0.
5.0. Preventative Maintenance
The laser head and adapter should never be stored or operated in an environment
having a high concentration of airborne particulates. Exposure to this condition may
cause interference with the feedback to the PIN detector that can ultimately cause
performance degradation or failure. Periodic inspection of the SFA output optical
surface is recommended.
The laser system must be turned off and disconnected from AC power before
inspecting the SFA output surface.
Remove the shutter from the SFA and look through its aperture under a fluorescent
light. The presence of any foreign matter is unacceptable. If it becomes necessary
to clean the optical surface, the following procedure should be used.
Using a clean cotton swab with reagent grade acetone or methanol. Gently clean the
surface of the beam splitter. Repeat the process twice to insure a clean surface.
Further service may be needed if a clean beam is not obtained.
Cleaning reagents may be hazardous. Please consult Material Safety Data
Sheets in accordance with any substances in use.
Internal optics assemblies can only be serviced by a factory authorized
service center.
13
IMPORTANT
IMPORTANT

Model N-STP Operation Manual
6.0. Operating Specifications
Table 1-1. Operating Specifications for Model N-STP Series
*Power Supply Model Dependent
14
Electrical
Parameter
Minimum
Typical
Maximum
Units
Model N-STP-910 or N-STP-912 Laser Head (with AC power supply)
Input Voltage*
104 or 207
126 or 264
VAC
Input Current*
0.48
A
Frequency
50
60
Hz
Model N-STP-910 Laser Head (DC Input)
Input Voltage
1220
VDC
Input Current
4.0
mA
Model N-STP-912 Laser Head (DC input)
Input Voltage
1600
VDC
Input Current
4.0
mA
SFA (With AC/DC Converter)
Input Voltage
90
264
VAC
Input Current
0.2/0.1
A
Frequency
50
60
Hz
Model N-STP-910/N-STP-912 System EMI (AC lines)
Conducted EMI 1-5 MHz
-50
-35
dbm
Mechanical
Model N-STP-910/ N-STP-912 Single Frequency Laser System
Temperature
Operating
15
35
C
Non-operating
-20
80
C
Humidity
Operating
0
90
%
Non-operating
0
90
%
Shock
Impulse (IEC68.2.27)
30x11
gxmsec
Vibration (IEC68.2.6)
10
55
Hz
Warm-up
15
40
minutes

Model N-STP Operation Manual
Table 1-1. Operating Specifications for Model N-STP Series (cont’d)
Optical
Model N-STP-910 Single Frequency Laser System
Parameter
Minimum
Typical
Maximum
Units
Output Range
Power (633 nm), Typical
0.35
0.70
mW
Frequency (v-vo (1))
400
600
MHz
Beam Diameter (1/e2)
0.48
mm
Beam Divergence (Full Angle)
1.70
mrad
Spatial Mode (TEM00)
100
%
Optical Noise
0.10
%RMS
Polarization
1000:1
5000:1
Model N-STP-912 Single Frequency Laser System
Output Range
Power (633 nm), Typical
0.60
1.40
mW
Frequency (v-vo (1))
50
600
MHz
Beam Diameter (1/e2)
0.54
mm
Beam Divergence (Full Angle)
1.50
mrad
Spatial Mode (TEM00)
100
%
Optical Noise
0.10
%RMS
Polarization
1000:1
5000:1
Power Stability
1 Hour
0.1
%
8 Hour
0.1
%
1 month
0.1
0.2
%
Frequency Stability 1
1Hour
1
MHz
8 Hour
1
MHz
1 Month
10
MHz
Notes:
1. See Section 8.0.
15

Model N-STP Operation Manual
Figure 1-5. Mechanical Specifications of Models N-STP-910 and N-STP-912
6.1. Laser Head Mounting
Figure 1-6. Recommended Mounting Areas
The laser head can be mounted by standard cylindrical laser head holders such as the Newport
ULM or ULM-TILT laser mount or by V-blocks at the recommended mounting areas (Figure 1-6).
16
MODEL
DIM A
Inch (mm)
DIM B
Inch (mm)
DIM C
Inch (mm)
N-STP-910
10.20 (259.1)
6.96 (176.8)
72.00 (1828.8)
N-STP-912
11.89 (302.0)
8.65 (219.7)
72.00 (1828.8)
LOCK RING
DIM
A
Stable/OT
ADAPTER
PLANE OF POLARIZATION
P
O
LA
RI
ZA
TI
O
N
PL
A
N
E
POTENTIOMETER
Output Adjust
1.70
BOTTOM VIEW
LEFT VIEW
RIGHT VIEW
TOP VIEW
AC/DC CONVERTER
100 VAC
115 VAC
230 VAC
240 VAC
OR
DIM
C
100 VAC
115 VAC
230 VAC
240 VAC
POWER SUPPLY LAB
OR
DIM
B
INPUT JACK
SFA ADAPTER
"STABLE/OT" LIGHT
LASER HEAD
2.70
INDICATOR LIGHT
OUTPUT JACK, STP-1
2.5mm ID 5.5mm OD
Center (+)
4.43
SWITCH
N-STP-910, 912
FRONT VIEW

Model N-STP Operation Manual
7.0. Output Power/Frequency Function
The output power or frequency of the Models N-STP-910 or N-STP-912 system can be
accurately tuned over a large portion of the available doppler gain profile.
Figure 1-7 shows actual output power versus optical frequency curves as measured
for the N-STP-910 and N-STP-912.
Figure 1-7. Output Power versus Optical Frequency Curves for the N-STP-910 and
N-STP-912
The differences in the shape is due to the very short cavity of the N-STP-910,
resulting in a narrower adjustment range of optical frequency.
17

Model N-STP Operation Manual
Normalized Output Power vs. Frequency
0
10
20
30
40
50
60
70
80
90
100
800
600
400
200
0
200
400
600
800
Frequency from Centerline (MHz)
Relative Output Power (% of Peak)
Curve 1
Curve 2
Figure 1-8. Normalized Output Power vs. Frequency normalized to have the
same peak power.
Curve 1: New tube; Curve 2: Tube near end-of-life.
Curve 2 depicts the doppler profile that exists at the end of the operating life if the laser tube
excitation parameter (total single pass gain/total losses) falls to 80% of its original value. This
gain decrease may be from gas cleanup or increased absorption loss changes of the cavity
mirrors. The peak output power available (at center-line) drops to nearly half its original
value.
If one normalizes both curves in Figure 1-8, it can be noted that this extreme degradation
does not appreciably affect the shape of the doppler curve. Thus, if one were to know the
peak value of output power (at center-line), a reasonably accurate calibration of output
frequency could be attained by using a power meter a calibration curve similar to Figure 1-7.
8.0. Frequency Calibration
As explained in Section 7.0, the Model N-STP-910, N-STP-912, single frequency laser system
may be tuned over a wide range of frequencies from center-line. Using calibration curves,
such as those shown in Figure 1-7, the output frequency can be calibrated to typically better
than 10% accuracy of a given frequency on the "Blue" side of the doppler output profile
for the 632.991 nm transition in 20Ne.
Figure 1-7 was constructed from measurements of a typical model N-STP-910 system
producing peak center-line power of about 1.3 mW and a typical model N-STP-912 system
producing peak center-line power of about 1.8 mW. As shown in Figure 1-8, the shape of
these curves will not deviate substantially over the useful life of the laser.
A laser power meter may be used for calibration by noting the peak center-line power during
the warm-up period while in the "Peak" detection mode. The desired frequency can then be
adjusted by looking up on the ordinate of Figure 1-7, the appropriate percentage of peak
center-line power for the desired frequency. By multiplying this percentage by the peak level
noted on the power meter, the output power may be adjusted for the desired frequency.
18