• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.40 no.8
• /
• pp.572-579
• /
• 2003

By comparing the measured optical reflection spectra with calculated one by the transfer-matrix method (TMM) in epitaxial wafers for vertical-cavity surface-emitting lasers (VCSELs), we have estimated the systematic thickness errors in a simple and nondestructive way. The experimentally confirmed technique is based on the finding that the shape of the reflection spectra depends mainly on a newly defined single parameter, the effective error in the n-mirror layers, and the thickness error in the active cavity simply shifts the Fabry-Perot resonance wavelength. Also shown is that the proposed method is reliable when the relative standard deviation of the random thickness errors is less than 0.005. Because reflection spectra are routinely measured, we can easily estimate the thickness errors nondestructively with high spatial resolution.

• Smart Structures and Systems
• /
• v.1 no.1
• /
• pp.63-82
• /
• 2005

This paper introduces a technology for robust and low maintenance cost sensor network capable to detect accelerations below a micro-g in a wide frequency bandwidth (above 1,000 Hz). Sensor networks with such performance are critical for navigation, seismology, acoustic sensing, and for the health monitoring of civil structures. The approach is based on the fabrication of an array of high sensitivity accelerometers, each utilizing Fabry-Perot cavity with wavelength-dependent reflectivity to allow embedded optical detection and serialization. The unique feature of the approach is that no local power source is required for each individual sensor. Instead one global light source is used, providing an input optical signal which propagates through an optical fiber network from sensor-to-sensor. The information from each sensor is embedded onto the transmitted light as an intrinsic wavelength division multiplexed signal. This optical "rainbow" of data is then assessed providing real-time sensing information from each sensor node in the network. This paper introduces the Fabry-Perot based accelerometer and examines its critical features, including the effects of imperfections and resolution estimates. It then presents serialization techniques for the creation of systems of arrayed sensors and examines the effects of serialization on sensor response. Finally, a fabrication process is proposed to create test structures for the critical components of the device, which are dynamically characterized.

• Korean Journal of Optics and Photonics
• /
• v.14 no.6
• /
• pp.674-679
• /
• 2003

We fabricated erbium-doped fiber ring laser with a new structure that can operate in C- & L-band wavelength region. The wave-length of the laser can be tuned continuously over 102 nm between 1510.4-1612.6 nm by insertion of the fiber Fabry-Perot tunable filter (FFP-TF) in the ring cavity. By use of the wavelength tunable characteristics of our fiber laser, we measured absorption spectra of more than fifty transition lines of the acetylene ($^{13}$ C$_2$H$_2$) molecule with high signal to noise ratio (SNR).

• Journal of the Optical Society of Korea
• /
• v.17 no.1
• /
• pp.33-37
• /
• 2013

In this study a new design concept of the Fabry-Perot filter, constructed with an anisotropic space layer and a couple of isotropic mirrors, was proposed based on the Maxwell equations and the characteristic matrix method. The single- and double-cavity Fabry-Perot filters were designed, and their optical properties were investigated with a developed software package. In addition, the dependence of the transmittance and phase shift for two orthogonal polarization states on the column angle of the anisotropic space layer and the incidence angle were discussed. We demonstrated that the polarization state of electromagnetic waves and phase shifts can be modulated by exploiting an anisotropic space layer in a polarization F-P filter. Birefringence of the anisotropic space layer provided a sophisticated phase modulation with varied incidence angles over a broad range, resulting in a wide-angle phase shift. This new concept would be useful for designing optical components with isotropic and anisotropic materials.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.10
• /
• pp.21-25
• /
• 2014

Scan capabilities of Fabry-Perot cavity (FPC) antennas are investigated for the case of a $4{\times}1$ thinned array placed inside the cavity. The FPC array antenna has higher maximum gain and lower sidelobe level (SLL), but the maximum scan angle of the thinned array is 14-17% lower than the patch array alone, due to increased mutual coupling in the FPC structures. However, unlike the bare thinned array, the SLL of FPC array does not suffer from the grating lobe problem even though it has a relative large element spacing of more than $1.0{\lambda}_0$.

• Journal of Sensor Science and Technology
• /
• v.23 no.2
• /
• pp.110-113
• /
• 2014

In this paper, we propose and demonstrate a Fabry-Perot interferometer (FPI) optical fiber tip sensor fabricated by a blade-sawing technique using a fiber optic patch cord for high-resolution temperature measurement. The sensor head consists of a short air FP cavity near the tip of a single-mode fiber patch cord tip. The temperature which we can measure is determined through a phase variation of the interference fringes in the reflective spectrum of the sensor. The fiber optic FPI sensor in this work can monitor the environmental temperature very accurately from 40 to $120^{\circ}C$. As a result, the temperature sensitivity is obtained as $38.2pm/^{\circ}C$.

• Journal of Sensor Science and Technology
• /
• v.30 no.4
• /
• pp.250-254
• /
• 2021

A highly sensitive and selective non-dispersive infrared (NDIR) carbon dioxide gas sensor requires achieving high transmittance and narrow full width at half maximum (FWHM), which depends on the interface of the optical filter for precise measurement of carbon dioxide concentration. This paper presents the design, simulation, and fabrication of a Fabry-Perot filter based on a distributed Bragg reflector (DBR) for a low-cost NDIR carbon dioxide sensor. The Fabry-Perot filter consists of upper and lower DBR pairs, which comprise multilayered stacks of alternating high- and low-index thin films, and a cavity layer for the resonance of incident light. As the number of DBR pairs inside the reflector increases, the FWHM of the transmitted light becomes narrower, but the transmittance of light decreases substantially. Therefore, it is essential to analyze the relationship between the FWHM and transmittance according to the number of DBR pairs. The DBR is made of silicon and silicon dioxide by RF magnetron sputtering on a glass wafer. After the optimal conditions based on simulation results were realized, the DBR exhibited a light transmittance of 38.5% at 4.26 ㎛ and an FWHM of 158 nm. The improved results substantiate the advantages of the low-cost and minimized process compared to expensive commercial filters.

• Proceedings of the Optical Society of Korea Conference
• /
• 2005.07a
• /
• pp.202-203
• /
• 2005

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.10a
• /
• pp.351-354
• /
• 2002

The new enhanced method of temperature control need not any reference temperature, the system itself can find the melting temperature of gallium as a reference point by dithering input heat flux. If gallium is in melting state, the latent heat of fusion works, so gallium temperature does not change on dithering input heat flux. Also, the control method can determine the state of gallium; solid, liquid, or melting state by investigating the temperature in gallium. We apply this new temperature stabilization method to stabilize a Fabry-Perot cavity, which serves as a ultimate length measurement technique. We achieved 1 mK-temperature stability and 1.5426 nm/ 95 mm-length stability over 10 hours.

• Journal of electromagnetic engineering and science
• /
• v.17 no.4
• /
• pp.241-243
• /
• 2017

In this paper, we have presented an equation for estimating the gain of a Fabry-Perot cavity (FPC) antenna with a finite dimension. When an FPC antenna has an infinite dimension and its height is half of a wavelength, the maximum gain of that FPC antenna can be obtained theoretically. If the FPC antenna does not have a dimension sufficient for multiple reflections between a partially reflective surface (PRS) and the ground, its gain must be less than that of an FPC antenna that has an infinite dimension. In addition, the gain of an FPC antenna increases as the dimension of a PRS increases and becomes saturated from a specific dimension. The specific dimension where the gain starts to saturate also gets larger as the reflection magnitude of the PRS becomes closer to one. Thus, it would be convenient to have a gain equation when considering the dimension of an FPC antenna in order to estimate the exact gain of the FPC antenna with a specific dimension. A gain versus the dimension of the FPC antenna for various reflection magnitudes of PRS has been simulated, and the modified gain equation is produced through the curve fitting of the full-wave simulation results. The resulting empirical gain equation of an FPC antenna whose PRS dimension is larger than $1.5{\lambda}_0$ has been obtained.