Technical Note:
Tunable Diode Lasers Definitions of Characteristics

Absolute Wavelength Accuracy

The maximum difference between the measured wavelength and the displayed wavelength of the laser system.

Amplified Spontaneous Emission (ASE)

The ratio of the optical power at the center of the laser linewidth to the optical power at a given distance, as measured using an optical spectrum analyzer with a set resolution bandwidth.

Coarse-Tuning Resolution

The smallest wavelength change you can make with the coarse-tuning DC motor on the TLB-6300 laser.

Current-Modulation Bandwidth

The highest rate at which the laser diode’s current can be changed. This is the 3-dB frequency of the direct-modulation input located at the laser head.

Fine-Frequency Modulation Bandwidth

The highest rate at which the fine-tuning PZT in the laser cavity can modulate the laser frequency. The specified bandwidth is for a 3-dB drop from a low-frequency baseline under small-signal modulation

Fine-Frequency Tuning Range

The frequency range over which the laser can be piezoelectrically tuned. (If l is the wavelength of the laser and c is the speed of light, the tuning range expressed in frequency, Dn, and wavelength, Dl, is related by Dn=c•Dl/l2. Keep in mind that 30 GHz
is equivalent to 1 cm–1.)

Integrated Dynamic Range

The ratio of the signal to the source emission, integrated overall wavelengths. This is measured by observing the spectrum of two cascaded fiber-Bragg gratings with a total rejection ratio of >100 dB and a 0.8-nm window, and is a realistic expectation of the dynamic range of your measurement. See Why is the Noise Spectrum Important? for more information.


The laser’s short-term frequency stability. The linewidth varies as a function of integration time.

Maximum Coarse-Tuning Speed

The highest guaranteed speed at which the TLB-6300 laser can tune using the coarse-tuning DC motor. The actual maximum coarse-tuning speed for individual systems may vary, but will always be at least this fast.

Minimum Power

The lowest power that the laser will output across its specified tuning range when the current is set to its recommended operating value. Due to changes in diode gain and cavity loss with wavelength, the laser’s output power is not constant as it tunes.

Output Power

The typical power that the laser will output across the entire tuning range.

Power Repeatability

The typical difference in power between scans for a given wavelength.

Power Stability

The maximum deviation in power as the laser sits at a specific wavelength over a 1-hour period.

Side-Mode Suppression Ratio

The ratio of the carrier to the nearest side mode

Tuning Range

The span of wavelengths over which the laser is guaranteed to operate mode-hop free. For the TLB-6300 series, the laser may be able to tune outside this range, but this may introduce mode hops.

Tuning Speed

The speed over which the laser can sweep over the entire tuning range.

Typical Maximum Power

The maximum output power you can expect over the laser’s tuning range. Due to changes in diode gain and cavity loss with wavelength, the laser’s output power is not constant as it tunes.

Wavelength Repeatability

The largest measured deviation that may occur when the laser returns to a given set wavelength. This is a measure of how well the laser returns to a set wavelength over many attempts and when approached from different directions.

Wavelength Resolution

The smallest step the laser can tune.

Wavelength Stability

The maximum amount of drift the laser will exhibit over a specified period of time and temperature variation.