• Technical Conference:  05 – 10 May 2024
  • The CLEO Hub: 07 – 09 May 2024

Visa Information

Visa Information

Letter of Invitation | Visa Information

Letter of Invitation

Please fill out all the required information on the online form completely to the best of your ability.

Important information

  • Your name must be listed exactly as it appears on your passport. Any differences between the name on your passport and the name on your invitation letter or other documentation could lead to a delay and/or denial of your visa. 
  • If you are presenting a paper, include the title and session in which the paper will be presented, or if you are exhibiting, please indicate so in your request.
  • Please note that each individual requesting an invitation letter must fill out a separate form. All letters will be sent in PDF form to the email address provided. If a paper letter is required, please respond to the email. Requested paper letters will be sent complimentary through airmail. This option may take a few weeks to arrive. If you wish to expedite the process, a letter will can be sent through Federal Express with the recipient’s Federal Express account number or credit card number with an expiration date. Please also include your billing address in the request email.
  • CLEO Management reserves the right to request further information regarding the company or affiliation of the attendee to ensure the validity of requests. Meeting attendees need not wait until their paper is accepted to request a Visa Invitation Letter.
  • CLEO is unable to contact U.S. Embassies in support of an individual attempting to gain entry to attend a meeting.
  • We recommend that you secure your travel visa before registering for the conference as cancellations after the preregistration cutoff may result in a cancellation fee.

Request a Visa Invitation Letter

Individuals requiring letters of invitation to obtain travel visas must apply using the online form.

For questions about the visa invitation letter application process, please send inquiries by email to invitations@optica.org or by mail to

CLEO Management – Invitation Letter
2010 Massachusetts Ave, NW
Washington, DC 20036
USA

Visa InformationClipart of a passport

Apply for Your Visa

The visa application process to enter the United States has become subject to greater degrees of scrutiny than in the past. For this reason, the application process can take up to six months or more. You will need to apply for your visa as early as possible, but no later than three months before you wish to enter the United States.

Generally, a citizen of a foreign country who wishes to enter the United States must first obtain a visa, either a nonimmigrant visa for temporary stay or an immigrant visa for permanent residence. Visitor visas are nonimmigrant visas for persons who want to enter the United States temporarily for business (visa category B-1), tourism, pleasure or visiting (visa category B-2), or a combination of both purposes (B-1/B-2).

There are several steps to apply for a visa. The order of these steps and how you complete them may vary at the U.S. Embassy or Consulate website where you will apply.

Visa Waiver Program

There are 39 countries that participate in the Visa Waiver Program. If your country is on this list, and you are traveling to the United States for tourism or business for 90 days or less with a valid passport that meets U.S. requirements, and the listed conditions do not apply to you, you do NOT need a visa. Otherwise, you need to obtain a visa.

Electronic System for Travel Authorization (ESTA)

ESTA is an automated system that determines the eligibility of visitors to travel to the United States under the Visa Waiver Program (VWP). Authorization via ESTA does not determine whether a traveler is admissible to the United States. U.S. Customs and Border Protection officers determine admissibility upon travelers' arrival. The ESTA application collects biographic information and answers to VWP eligibility questions. ESTA applications may be submitted at any time prior to travel, though it is recommended that travelers apply as soon as they begin preparing travel plans or prior to purchasing airline tickets.

Please note under new changes, the following categories of travelers are no longer eligible to travel or be admitted to the United States under the Visa Waiver Program, and will need to apply for, and go through the standard Visa application and interview process:

  • Nationals of VWP countries who have traveled or been present in Iran, Iraq, North Korea, Sudan, Syria, Libya, Somalia and/or Yemen on or after 01 March 2011 (with limited exceptions)
  • Nationals of VWP countries who are also nationals of Iran, Iraq, North Korea, Sudan or Syria. 

If you are in either category, you will need to apply for and go through the standard visa application and interview process.

Complete an ESTA application. >

Visa Application Guidelines

Complete the Online Visa Application

  • Online Nonimmigrant Visa Application, Form DS-160Learn more about completing the DS-160. You must:
    • Complete the online visa application.
    • Print the application form confirmation page to bring to your interview.
  • Photo — You will upload your photo while completing the online Form DS-160. Your photo must be in the format explained in the Photograph Requirements.

Schedule an Interview

Personal interviews can be critical to successfully and efficiently obtaining a visa to enter the United States. One factor contributing to the increase in the processing time is a personal interview that is now required for most applicants as a standard part of visa processing. Group interviews are not recommended. Applicants need to be prepared to clearly present their intent to return from the U.S. as well as explain in detail how they will be spending their time while in the United States. It is not enough to state, “I will be attending a meeting.” Embassies are looking for more details as well as documents and information that demonstrate and support these intents.

Individuals are strongly encouraged to contact the embassy or consulate to schedule a personal interview as soon as it is known a visa is necessary for travel. Be aware that it may be difficult to qualify for a visa outside of your place of permanent residence. Wait times for interview appointments vary by location, season and visa category, so you should apply for your visa early.

Prepare for Your Interview

There will be a non-refundable visa application fee. Review the instructions available on the website of the U.S. Embassy or Consulate where you will apply to learn more about the fee payment.

  • Gather required documentation
    • Passport valid for travel to the United States — Your passport must be valid for at least six months beyond your period of stay in the United States, unless exempt by country-specific agreements. If more than one person is included in your passport, each person who needs a visa must submit a separate application.
    • Nonimmigrant Visa Application, Form DS-160 confirmation page
    • Application fee payment receipt, if you are required to pay before your interview
    • Photo — You will upload your photo while completing the online Form DS-160. If the photo upload fails, you must bring one printed photo in the format explained in the Photograph Requirements.
    • Additional documents may be requested to establish if you are qualified. Additional requested documents may include evidence of:
      • The purpose of your trip
      • Your intent to depart the United States after your trip
      • Your ability to pay all costs of the trip
      • Evidence of your employment and/or your family ties may be sufficient to show the purpose of your trip and your intent to return to your home country. If you cannot cover all the costs for your trip, you may show evidence that another person will cover some or all costs for your trip.

Note: Visa applicants must qualify on the basis of the applicant's residence and ties abroad rather than assurances from U.S. family and friends. A letter of invitation or Affidavit of Support is not needed to apply for a nonimmigrant tourist visa. If you do choose to bring a letter of invitation or Affidavit of Support to your interview, please remember that it is not one of the factors in use in determining whether to issue or deny a nonimmigrant tourist visa.

Attend Your Interview

During your visa interview, a consular officer will determine whether you are qualified to receive a visa, and if so, which visa category is appropriate based on your purpose of travel. You will need to establish that you meet the requirements under U.S. law to receive the category of visa for which you are applying. Ink-free, digital fingerprint scans will be taken as part of your application process. They are usually taken during your interview, but this varies based on location.

After your visa interview, your application may require further administrative processing. (You will be informed by the consular officer if further processing is necessary for your application.) When the visa is approved, you may pay a visa issuance fee if applicable to your nationality and will be informed how your passport with visa will be returned to you.

Review the visa processing time to learn how soon your passport with visa will generally be ready for pick-up or delivery.

Visa Renewals

Whether you are applying for the first time or renewing your visa, you will use the same application process. Some applicants seeking to renew their visas in certain visa classes may be eligible for the Interview Waiver Program (IWP),  which allows qualified individuals to apply for visa renewals without being interviewed in person by a U.S. consular officer. Review the instructions on the website of the U.S. Embassy or Consulate where you will apply to determine if the IWP is available and if you qualify.

Online Resources

CLEO Management is not able to contact U.S. Embassies in support of an individual attempting to gain entry into the host country to attend the conference.

If your visa is delayed or denied, please contact the consulate where your application is being processed. Review Visa Denials for detailed information about visa ineligibilities, denials and waivers.

Visitors are not permitted to accept employment or work in the United States.

Unless canceled or revoked, a visa is valid until its expiration date. Therefore, a valid U.S. visa in an expired passport is still valid. If you have a valid visa in your expired passport, do not remove it from your expired passport. You may use your valid visa in your expired passport along with a new valid passport for travel and admission to the United States.