All polarization-maintaining Er fiber-based optical frequency combs with nonlinear amplifying loop mirror.

A fully stabilized all polarization-maintaining Er frequency comb with a nonlinear amplifying loop mirror with below 0.2 rad carrier-envelope-offset frequency phase noise is demonstrated. The integrated timing jitter is measured as 40 attosecond from 10 kHz to 10 MHz, which is the lowest value of any Er fiber frequency comb to date.

Ultra-low noise all polarization-maintaining Er fiber-based optical frequency combs facilitated with a graphene modulator.

High bandwidth carrier phase and repetition rate control are critical for the construction of low phase noise optical frequency combs. Here we demonstrate the use of a graphene modulator for the former and a bulk electro-optic modulator for the latter enabling record low phase noise operation of an Er fiber frequency comb. For applications that do not require carrier phase control, we show that the form factor of a fiber comb can be reduced by adapting a graphene modulator for rapid repetition rate control. Moreover, the whole system demonstration is performed with all-polarization maintaining Er fiber frequency combs, highly suitable for applications in the field.

Familial interstitial pneumonia in an adolescent boy with surfactant protein C gene (Y104H) mutation.

Recent studies have suggested that some cases of familial interstitial pneumonia are associated with mutations in the gene encoding surfactant protein C (SFTPC). We report here a case of familial interstitial pneumonia in an adolescent boy whose paternal grandfather and father suffered from idiopathic interstitial pneumonia (IIP). The patient was asymptomatic but showed an abnormal shadow in the chest at his medical check-up. The surgical biopsy of the patient revealed non-specific interstitial pneumonia and showed pathological findings similar to those in his father's autopsy. Genomic DNA from blood leucocytes of the patient was sequenced for the Thy104His (Y104H) SFTPC mutation. Based on these results, he was diagnosed with SFTPC mutation-associated familial interstitial pneumonia. There has been no clinical, physiologic and radiologic progression for 4 years since the diagnosis. The relation between clinical manifestation and the mutation site of the patient may broaden the spectrum of SFTPC mutation-associated interstitial pneumonia.

A photonic frequency discriminator based on a two wavelength delayed self-heterodyne interferometer for low phase noise tunable micro/mm wave synthesis.

Low phase noise frequency synthesizers are of paramount interest in many areas of micro-mm wave technology, encompassing for example advanced wireless communication, radar, radio-astronomy, and precision instrumentation. Although this broad research field is not bereft of methods for the generation of either low phase noise micro- or mm waves, no universal system applicable to low phase noise generation for micro and mm waves has yet been demonstrated. Here we propose a new photonic frequency discriminator based on a two wavelength delayed self-heterodyne interferometer which is compatible with such an objective. The photonic frequency discriminator can be a reference both for micro and mm waves to lower their phase noise. As a proof-of-concept, we demonstrate a low phase noise tunable OEO (6-18 GHz) and locking of a heterodyne beat between two cw lasers (10-400 GHz) with low relative phase noise. The required components for the photonic frequency discriminator are off-the-shelf and can be readily assembled. We believe this new type of photonic frequency discriminator will enable a new generation of universal precision tunable sources for the X, K, V, W and mm-bands and beyond.

Electro-optic comb based real time ultra-high sensitivity phase noise measurement system for high frequency microwaves.

Recent progress in ultra low phase noise microwave generation indispensably depends on ultra low phase noise characterization systems. However, achieving high sensitivity currently relies on time consuming averaging via cross correlation, which sometimes even underestimates phase noise because of residual correlations. Moreover, extending high sensitivity phase noise measurements to microwaves beyond 10 GHz is very difficult because of the lack of suitable high frequency microwave components. In this work, we introduce a delayed self-heterodyne method in conjunction with sensitivity enhancement via the use of higher order comb modes from an electro-optic comb for ultra-high sensitivity phase noise measurements. The method obviates the need for any high frequency RF components and has a frequency measurement range limited only by the bandwidth (100 GHz) of current electro-optic modulators. The estimated noise floor is as low as -133 dBc/Hz, -155 dBc/Hz, -170 dBc/Hz and -171 dBc/Hz without cross correlation at 1 kHz, 10 kHz, 100 kHz and 1 MHz Fourier offset frequency for a 10 GHz carrier, respectively. Moreover, since no cross correlation is necessary, RF oscillator phase noise can be directly suppressed via feedback up to 100 kHz frequency offset.