Cavity scanning

Both of these are routine tasks when FM is employed. The relative magnitudes of the cavity background signals with- and without the sample present give T/To. Ql is determined from a scan, for which the source and cavity frequencies are maintained at the sample resonance whilst the FM deviation is scanned de-crementally from its upper value to near zero. The servo loop is unable to maintain the lock at zero deviation, hence the direction of scan. Examples of a series of scans for various values of the FM depth on the cavity at resonance frequency 175 GHz are shown in Figure 6.15. These cavity scans show a broad maximum whose value reflects the Q of the cavity. 

The resulting data have been found to give consistently good fits to a formula derived by Baker et al. making it possible to determine the loaded-Q to a precision of 0.1%. The derivation of this formula is not trivial and will not be reproduced here. The maximum of the cavity scan curve described there occurs when the ratio m of the FM deviation Av to the cavity resonance bandwidth equals 2.2. This can be used simply to find an approximate value for the Q. As Q... 

Fig. 15. (a) The transmission with the empty cavity and EIT medium inside the cavity, (b) The required minimum cavity scan speed as a function of cavity decay. The black dashed line is for an empty cavity and the blue solid Une is for the cavity with an intracavity EIT medium The parameters are used ... 

For an empty cavity the round-trip phase shift is just determined by the length of the cavity and can by expressed as = k(L + vt), where k is the wave number of the cavity field and v is the cavity scan speed. So the intracavity field can be analytically solved to give iikvt+iKf ... 

In such case, the effective cavity finesse is increased by a factor of (X + rj). Thus, the required cavity scan speed to observe CRE for a cavity with an intracavity EIT medimn can be much... 

The guide wavelength can differ markedly from the free-space wavelength A and so wavelengths measured on this basis must be carefully corrected. This requires an absolute identification of the mode in question, which is not so in the Fabry-Perot resonator case, where modes with fixed values of p and / reappear with the same periodicity (very nearly) as do modes with any other fixed values of p and /. For example in Fig. 3.4, which is a cavity scan made with a circular metallic waveguide laser of 19mm diameter, many different periodicities... 

Fig. 3.4. Segment of a cavity scan, or Laser Resonator Interferogram , in this case for a waveguide laser. Despite the many peaks only two distinct laser transitions are involved — at 447 /im and 1306 fim free space wavelength. The marked features have the following guide wavelengths A and B — 447 //m, C—1310 //m, D— 1346/im. The gas was ethyl chloride and the pump line 10J728. Adapted from [3.9] by the author.

This 67-year-old patient was optimally debulked and completed six cycles of paclitaxel/carboplatin after her surgery. HerCA-125 normalized (12 U/mL, 12 kU/L) on completion of her chemotherapy treatment, and her CT scan was negative. This patient returns to your clinic for her first 3-month follow-up appointment. Her CA-125 is (45 U/mL, 45 kU/L), and she reports some mild bloating. CT scan report states mild fluid accumulation in the pelvic cavity. 

The SEEPR technique allows the simultaneous recording of the CV and the CW EPR spectrum of the radicals produced during the electron transfer reactions (Khaled et al. 1991). The SEEPR technique consists of an IBM enhanced electrolytic cell inserted in a rotating cylindrical EPR cavity. The cell is no longer sold by IBM, but a description can be found (Khaled et al. 1990, 1991). The CVs were obtained using a commercial (BAS-100) electrochemical analyzer while simultaneously recording the EPR spectra during the scan. 

These structures were recorded by a vectorial focal spot scanning in a spiral-by-spiral method rather in a raster layer-by-layer mode using a PZT stage. Such spiral structures fabricated in SU-8 have optical spot bands in near-lR [24], telecommunication [25], and 2-5 pm-IR region [26] or can be used as templates for Si infiltration [11]. It is obvious, that direct laser scanning is well suited for defect introduction into 3D PhC, as demonstrated in resin where a missing rod of a logpUe structure resulted in the appearance of a cavity mode in an optical transmission spectriun [27]. 

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