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Mid-IR Laser Sources: 2.7 µm
Shown above is the output beam of an LFL2700 mid-IR laser source, collimated using an RC02APC-P01 reflective collimator. The output is delivered to the colimator using a P3-23Z-FC-1 mid-IR single mode patch cable.
Thorlabs' LFL2700 turnkey fiber-coupled fiber laser sources are reliable and easy to operate, featuring high brightness and an emission wavelength centered near 2.7 µm. Incorporating an erbium-doped ZrF4 fiber laser, these mid-IR laser sources are ideal for test and measurement applications. Models are available with maximum output powers of >5 mW (LFL2700-5), >10 mW (LFL2700-10), or >30 mW (LFL2700). Compared to antimonide-based laser diodes at this wavelength, these mid-IR laser sources are more powerful and offer superior mode and beam quality.
The modulation capability of the LFL2700 lasers enables the use of lock-in detection techniques to reduce measurement noise and to improve detection sensitivity. This capability, combined with a single-mode, high-brightness beam, makes the laser ideal for high-dynamic range measurements, such as polarization extinction ratio or power isolation measurements.
The laser output of our LFL2700-10 and LFL2700 mid-IR laser sources can be modulated at frequencies up to 40 kHz using an external modulation input; see the Modulation tab for more details and examples of possible modulated laser outputs. Please note that the LFL2700-5 mid-IR laser source does not support modulation. Thorlabs' mid-IR FC/APC-compatible patch cables using zirconium fluoride fiber (for example, Item # P3-23Z-FC-1) are ideal for connecting the output of these laser sources to other fiber-coupled devices or free-space optics. Please note that the up-conversion process in the Er-doped fiber will also produce green fluorescence. A small amount of this fluorescence is guided in the fiber to the output port of the laser. The power level of the green fluorescence exiting the output port is approximately 10 µW (typical). In applications where the green light is undesirable, it can be filtered out using a MIR filter or by using an AR coated MIR window with no transmission in the visible range, such as Germanium or Silicon windows.
An intuitive LCD interface allows the user to view and set the parameters for the fiber laser. The user can adjust the drive current of the pump laser to control the fiber laser output power; each laser is shipped with test data that shows output power scaling as a function of the pump drive current. A USB interface allows control of the laser source through a command line interface. Please see the Software tab for Windows drivers. Each laser source also includes a universal power supply, operating at 100 to 240 VAC without the need for selecting the voltage.
Mid-IR Laser Source Block Diagram
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Due to the Fabry-Perot nature of the cavity and mode competition, multiple modes within the gain bandwidth fade in and out. The total long-term spectral width of the emission band is <1.5 nm (RMS). This sample measurement was made by calculating an average of twenty traces, then applying a 6-point moving average to the twenty-trace average. The data was obtained using Thorlabs' Optical Spectrum Analyzer with a resolution of 180 pm. The 5 mW LFL2700-5 and 10 mW LFL2700-10 mid-IR fiber laser sources produce similar spectra to the 30 mW LFL2700 mid-IR fiber laser source. The spectrum curve of each source is measured and provided on an individualized item data sheet that ships with each item.
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These L-I curves provide an example of how the output power varies with the pump current, which is adjustable via the knob on the front panel of each source. Note that the LFL2700-5 mid-IR fiber laser source has a maximum pump laser drive current of 500 mA. The L-I curve for each source is measured and provided on an individualized item data sheet that ships with each item.
The plots below show the laser output intensity with an external modulation waveform applied to an LFL2700 mid-IR fiber laser source. Note that only the LFL2700-10 and LFL2700 mid-IR fiber laser sources support modulation. It is necessary to carefully tune the input waveform parameters until the desired modulated laser output is achieved. For example, the amplitude and DC offset can be adjusted until the maximum modulation depth is obtained. The output can be modulated using waveforms with frequency components up to 40 kHz; however, the full modulation depth is only achievable up to 2 kHz. The modulation is ideal for sensitive detection using a lock-in amplifier.
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