The output conductance of this equivalent two-port is equal to the conductance of
the photodetector with the transfer function of RF FODL. The more complicate
mathematical model, in which a laser is presented by semiclassical equations and
takes into consideration the laser optical emission noises and its conversion into the
RF phase noise, is discussed in Chap. 7 of this book.
2.7 Modern Elements of OEO: A Laser, the Optical Fiber,
and a Photodetector
In describing OEO system, the important role in achievement of the minimal phase
noise level is played by RF FODL elements: the laser with included optical resonators and discriminator, the optical fiber, and the photodetector. In this section, we
briefly discuss the most important key problems, which solution leads to the record
minimal characteristic of the phase noise.
2.7.1 A Laser
Utilization as a laser of the nanostructured quantum-well laser diode in OEO leads to
qualitatively new properties of OEO. Due to “quantization of zones in the transition,” as we show in Chaps. 4 and 5 of this book, the quality of optical emission
changes: the level of noisy spontaneous emission reduces more than 100 times, and
due to this, phase and amplitude noises of the laser significantly reduce, the optical
emission spectral line decreases from several gigahertz to several kilohertz. In
addition, the emission directivity pattern becomes narrower and polarization characteristics improve.
Besides the transition from the 3D semiconductor structures to the quantum-well
laser with minimal phase noises, the choice of optical resonator plays the significant
role. At that, the line width (on the level of half-power) of the resonance curve of
promising lasers should achieve 1–1000 kHz.
2.7.2 Optical Resonators and the Optical Fiber
Experimental characteristics of main modern optical resonators are illustrated in
Table 2.1 and in Fig. 2.7. As shown in Table 2.1, disk resonators have the maximum
Q-factor [32–36]: Q ¼ 8 Â 10
9 on SiO 2 , and Q ¼ 8 Â 10
15 on CaF 2 . Their
disadvantages are:
2.7 Modern Elements of OEO: A Laser, the Optical Fiber, and a Photodetector
39
the photodetector with the transfer function of RF FODL. The more complicate
mathematical model, in which a laser is presented by semiclassical equations and
takes into consideration the laser optical emission noises and its conversion into the
RF phase noise, is discussed in Chap. 7 of this book.
2.7 Modern Elements of OEO: A Laser, the Optical Fiber,
and a Photodetector
In describing OEO system, the important role in achievement of the minimal phase
noise level is played by RF FODL elements: the laser with included optical resonators and discriminator, the optical fiber, and the photodetector. In this section, we
briefly discuss the most important key problems, which solution leads to the record
minimal characteristic of the phase noise.
2.7.1 A Laser
Utilization as a laser of the nanostructured quantum-well laser diode in OEO leads to
qualitatively new properties of OEO. Due to “quantization of zones in the transition,” as we show in Chaps. 4 and 5 of this book, the quality of optical emission
changes: the level of noisy spontaneous emission reduces more than 100 times, and
due to this, phase and amplitude noises of the laser significantly reduce, the optical
emission spectral line decreases from several gigahertz to several kilohertz. In
addition, the emission directivity pattern becomes narrower and polarization characteristics improve.
Besides the transition from the 3D semiconductor structures to the quantum-well
laser with minimal phase noises, the choice of optical resonator plays the significant
role. At that, the line width (on the level of half-power) of the resonance curve of
promising lasers should achieve 1–1000 kHz.
2.7.2 Optical Resonators and the Optical Fiber
Experimental characteristics of main modern optical resonators are illustrated in
Table 2.1 and in Fig. 2.7. As shown in Table 2.1, disk resonators have the maximum
Q-factor [32–36]: Q ¼ 8 Â 10
9 on SiO 2 , and Q ¼ 8 Â 10
15 on CaF 2 . Their
disadvantages are:
2.7 Modern Elements of OEO: A Laser, the Optical Fiber, and a Photodetector
39