We demonstrate a Fourier domain mode locked (FDML) laser centered at 1190 nm with 2×410 kHz sweep repetition rate, a sweeping range of 100 nm and 2.5 mW output power. The laser is based on a quantum dot-semiconductor optical amplifier with small linewidth enhancement factor. The laser could be used as a probe laser in stimulated Raman scattering microscopy and it may be attractive for optical coherence tomography due to low water absorption and the spectral signature of lipids around 1200nm. Moreover, it is ideal to close the gap between FDML lasers at 1064 nm and 1300 nm. Combining these three lasers can enable ultrawideband sweeping to improve the axial OCT resolution down to 2 μm.
We demonstrate a Fourier domain mode locked (FDML) laser centered around 850 nm with a sweeping range of 50 nm, a fundamental repetition rate of 2×416 kHz and an output power of 2 mW. A new cavity design using three chirped Fiber Bragg gratings is required to overcome sweeping limitations caused by high dispersion. Other solutions to address challenges such as high loss and high polarization mode dispersion will be discussed along with performance. A main application of this laser will be retinal imaging, but it might also be applicable for TiCo-Raman and SLIDE microscopy.
The chromatic dispersion in optical fibers is a key property for applications where a broadband light source is used and the timing of each individual wavelength is crucial. Counteracting the timing offset introduced by the fiber is a challenge in many applications especially in mode locked lasers. The dispersion parameters need to be measured with high precision. The length of the fiber, the temperature, and the used wavelength will highly impact the amount of dispersion and the accuracy of the measurement. We developed an ultra-high-accuracy dispersion measurement setup at 1080 ± 50 nm considering all the parameters that may influence the measurement. It is based on a home-built wavelength tunable laser where the output is modulated by an electro-optical modulator connected to a 24 GSamples/s arbitrary waveform generator to a complex pattern consisting of pulses and a 4 GHz sine wave. After passing through the fiber the signal is measured with an 80 GSamples/s real time oscilloscope. The fiber’s temperature is controlled to allow for reproducible measurements over several days and we achieve timing measurement accuracies down to ~200 fs. We also present the performance of the setup at ~850 nm. We will discuss and quantify all effects which can negatively impact the system accuracy and we will report on more cost-effective options using lower performance equipment.
Non-invasive identification, understanding and evaluation of articular cartilage damage is paramount for osteoarthritis researcher and clinician alike. Using polarisation sensitive optical coherence tomography together with impact and creep load, we use a range of metrics including birefringence to detect early signs of cartilage degeneration and gain new insights into the physiology of joint tissues
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