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Benchtop SLD Light Sources
SM Fiber Coupled,
PM Fiber Coupled,
Thorlabs' Fiber-Coupled SLD Sources are benchtop units that have an integrated superluminescent diode (SLD), controller, and TEC. These sources produce broadband emission centered at 1050 nm, 1310 nm, or 1550 nm and the output is coupled to an FC/APC connector. The center wavelength with these devices, as with all broadband devices, is defined by an average weighted by the relative amplitude and may not correspond to peak power or the FWHM center wavelength due to the asymmetry of the spectrum.
The 1050 nm SLD source is available with PM fiber output, while the other wavelengths are available from stock with either SM or PM fiber outputs. See the tables to the right for a summary of available sources. Please note that optical feedback can diminish the output power or damage the SLD source. We do not recommend using these SLD sources with components that are prone to back reflections, such as FC/PC connectors. Custom units with different connectors, fibers, or an optical isolator incorporated into the unit are available upon request by contacting Tech Support.
An intuitive LCD interface on the front of the unit allows the user to view the parameters for the SLD. For more details, please see the Operation tab. A USB 2.0 connector is provided for remotely enabling the SLD and adjusting the temperature and power. On the rear panel, an analog input is available to modulate the SLD with an external signal of 0 to 5 V, which is added to the internal setpoint. To prevent damage, an integrated microcontroller will disable the output if the analog input plus the internal setpoint exceeds the SLD limits.
The SLDs in these benchtop sources are operated using an independent, high-precision, low-noise constant current source and temperature control unit. The integrated microcontroller fully regulates the SLD's optical power and temperature as well as monitors the system for fault conditions.
Superluminescent diodes are excellent high-power broadband light sources for use in applications such as Optical Coherence Tomography (OCT) and Fiber Optic Gyroscopes (FOG). The SLDs offered here are indium phosphide (InP) devices. For safety, most of Thorlabs' SLDs are designed with housing that meets 3B laser requirements; with a key switch, 3B compliant interlocking features, an installed dust cap, and a power on warning with a five second blinking light. Furthermore, the color of the LED will not interfere with laser glass. To see which SLDs have 3B compliant housing, see below. For more information on what 3B compliance is, please refer to the Laser Safety tab.
The S5FC includes a universal power supply allowing operation over 100 to 240 VAC without the need for selecting the line voltage. The fuse access is conveniently located on the rear panel.
We also offer custom wavelength benchtop SLD sources to meet the needs of customers whose applications are not covered by our stock selection. Contact Tech Support for more information.
Thorlabs' SLDs use a single four quadrant LCD to display information as shown in the photograph to the right (Digital Display with Backlight).
Adjusting the SLD Output Power and Temperature
The control knob/switch utilizes an intelligent speed control. Turning the knob slowly corresponds to fine adjustment while turning the knob quickly corresponds to coarse adjustment. The SLD current threshold is a user-selectable command parameter that allows the user to filter out nonlinear sections of the SLD power curve. The threshold current is defaulted to 1 mA on initial power up.
The unit will be in Display Mode when it is first turned on to show the variables such as power reading, temperature, and wavelength. Pressing the control knob/switch once enables the Current Control Mode. Simply turn the knob will allow the user to adjust the current. Pressing the control knob one more time enables Temperature Control Mode. The user will be able to adjust temperature in this mode. The resolution for the current adjustment is 0.1 mA and 0.01 °C for temperature adjustment.
Modulating the SLD Output
The Analog In input can be used to modulate the SLD output or to set the SLD output remotely using a 5 V power source. The 5 V maximum input corresponds to the maximum calibrated power, which operates the SLD using a constant current drive technique. The resulting actual output power is dependent on the set current and operating temperature.
In addition, in order to eliminate a dead zone in the power control knob, the output of the unit is offset to the threshold current of the coupled SLD diode. Adjusting the knob below threshold will immediately set the current to 0.0 mA, or Standby mode. Therefore, there are two modes of modulation available. First, setting the control to "Standby" allows the analog modulation to utilize the full 0 to 5 V input range. The drawback is that a minimum voltage will be required to operate above the threshold current but allows more flexibility by the user. The second mode is to adjust the control knob so that the SLD is at threshold or above. The analog modulation voltage will be limited to less than the full 0 to 5 V range, but a DC offset will not be required. This should be kept in mind when using the modulation input since it will limit the actual input voltage range.
Making the Safety Interlock Connections
The S5FC series of SLD sources are equipped with a remote interlock connector located on the rear panel. All units have this feature regardless of their FDA and IEC classifications. In order to enable the S5FC source, a short circuit must be applied across the terminals of the Remote Interlock connector. In practice this connection is made available to allow the user to connect a remote-actuated switch to the connector (i.e., an open door indicator). The switch (which must be normally open) has to be closed in order for the unit to be enabled. Once the switch is in an open state, the S5FC source will automatically shut down. If the switch returns to a closed condition, the S5FC source must be re-enabled at the unit by pressing the ENABLE switch.
0 to 5 V
Remote Interlock Input
2.5 mm Mono Phono Jack
Terminals must be shorted either by included plug or user device, i.e. external switch, for laser mode "ON" to be enabled.
USB Type B
USB Type A to Type B Cable Included
Laser Safety and Classification
Safe practices and proper usage of safety equipment should be taken into consideration when operating lasers. The eye is susceptible to injury, even from very low levels of laser light. Thorlabs offers a range of laser safety accessories that can be used to reduce the risk of accidents or injuries. Laser emission in the visible and near infrared spectral ranges has the greatest potential for retinal injury, as the cornea and lens are transparent to those wavelengths, and the lens can focus the laser energy onto the retina.
Safe Practices and Light Safety Accessories
Lasers are categorized into different classes according to their ability to cause eye and other damage. The International Electrotechnical Commission (IEC) is a global organization that prepares and publishes international standards for all electrical, electronic, and related technologies. The IEC document 60825-1 outlines the safety of laser products. A description of each class of laser is given below: